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19 (nineteen) is the
natural number In mathematics, the natural numbers are those numbers used for counting (as in "there are ''six'' coins on the table") and ordering (as in "this is the ''third'' largest city in the country"). Numbers used for counting are called ''cardinal ...
following 18 and preceding 20. It is a
prime number A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways ...
.


Mathematics

19 is the eighth
prime number A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways ...
, and forms a
sexy prime In number theory, sexy primes are prime numbers that differ from each other by 6. For example, the numbers 5 and 11 are both sexy primes, because both are prime and . The term "sexy prime" is a pun stemming from the Latin word for six: . If o ...
with 13, a
twin prime A twin prime is a prime number that is either 2 less or 2 more than another prime number—for example, either member of the twin prime pair (41, 43). In other words, a twin prime is a prime that has a prime gap of two. Sometimes the term ''twin p ...
with 17, and a
cousin prime In number theory, cousin primes are prime numbers that differ by four. Compare this with twin primes, pairs of prime numbers that differ by two, and sexy primes, pairs of prime numbers that differ by six. The cousin primes (sequences and in O ...
with 23. It is the third full reptend prime, the fifth central trinomial coefficient, and the seventh
Mersenne prime In mathematics, a Mersenne prime is a prime number that is one less than a power of two. That is, it is a prime number of the form for some integer . They are named after Marin Mersenne, a French Minim friar, who studied them in the early 17th ...
exponent. It is also the second
Keith number In number theory, a Keith number or repfigit number (short for repetitive Fibonacci-like digit) is a natural number n in a given number base b with k digits such that when a sequence is created such that the first k terms are the k digits of n and ...
, and more specifically the first Keith prime. * 19 is the maximum number of fourth powers needed to sum up to any natural number, and in the context of
Waring's problem In number theory, Waring's problem asks whether each natural number ''k'' has an associated positive integer ''s'' such that every natural number is the sum of at most ''s'' natural numbers raised to the power ''k''. For example, every natural numb ...
, 19 is the fourth value of g(k). * The sum of the squares of the first 19 primes is divisible by 19. *19 is the sixth Heegner number. 67 and 163, respectively the 19th and 38th prime numbers, are the two largest Heegner numbers, of
nine 9 is a number, numeral, and glyph. 9 or nine may also refer to: Dates * AD 9, the ninth year of the AD era * 9 BC, the ninth year before the AD era * 9, numerical symbol for the month of September Places * Nine, Portugal, a parish in the ...
total. * 19 is the third
centered triangular number A centered (or centred) triangular number is a centered figurate number that represents an equilateral triangle with a dot in the center and all its other dots surrounding the center in successive equilateral triangular layers. The followin ...
as well as the third centered hexagonal number. : The 19th
triangular number A triangular number or triangle number counts objects arranged in an equilateral triangle. Triangular numbers are a type of figurate number, other examples being square numbers and cube numbers. The th triangular number is the number of dots i ...
is
190 Year 190 ( CXC) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Aurelius and Sura (or, less frequently, year 943 ''Ab urbe condita'' ...
, equivalently the sum of the first 19 non-zero
integer An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign ( −1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the languag ...
s, that is also the sixth centered nonagonal number. :19 is the first number in an infinite sequence of numbers whose digits start with 1 and have trailing 9's, that form triangular numbers containing trailing zeroes in proportion to 9s present in the original number; i.e. 19900 is the 199th triangular number, and 1999000 is the 1999th. :Like 19, 199 and 1999 are also both prime, as are 199999 and 19999999. In fact, a number of the form 19''n'', where ''n'' denotes the number of nines that terminate in the number, is prime for ''n'' = 1, 2, 3, 5, 7, 26, 27, 53, 147, 236, 248, 386, 401. * 19, alongside 109, 1009, and 10009, are all prime (with 109 also full reptend), and form part of a sequence of numbers where inserting a digit inside the previous term produces the next smallest prime possible, up to scale, with the
composite Composite or compositing may refer to: Materials * Composite material, a material that is made from several different substances ** Metal matrix composite, composed of metal and other parts ** Cermet, a composite of ceramic and metallic materials ...
number 9 as root. 100019 is the next such smallest prime number, by the insertion of a 1. :Numbers of the form 10''n''9 equivalent to 10''x'' + 9, where ''n'' denotes the number of
zero 0 (zero) is a number representing an empty quantity. In place-value notation such as the Hindu–Arabic numeral system, 0 also serves as a placeholder numerical digit, which works by multiplying digits to the left of 0 by the radix, usual ...
s in the term, are prime for ''n'' = , and probably prime for ''n'' = ; with ''x'' = ''n'' + 1. * 19 is the first prime number that is not a
permutable prime A permutable prime, also known as anagrammatic prime, is a prime number which, in a given base, can have its digits' positions switched through any permutation and still be a prime number. H. E. Richert, who is supposedly the first to study the ...
, as its reverse ( 91) is
composite Composite or compositing may refer to: Materials * Composite material, a material that is made from several different substances ** Metal matrix composite, composed of metal and other parts ** Cermet, a composite of ceramic and metallic materials ...
. 19 x 91 =
1729 Events January–March * January 8 – Frederick, the eldest son of King George II of Great Britain is made Prince of Wales at the age of 21, a few months after he comes to Britain for the first time after growing up in Hano ...
, the first
Hardy-Ramanujan number 1729 is the natural number following 1728 and preceding 1730. It is a taxicab number, and is variously known as Ramanujan's number and the Ramanujan-Hardy number, after an anecdote of the British mathematician G. H. Hardy when he visited Indian ma ...
or taxicab number, also a Harshad number, as it's divisible by the sum of its digits, 19. 91 is also the fourth centered nonagonal number. * The only nontrivial normal magic hexagon is composed of nineteen cells, where every diagonal of consecutive hexagons has sums equal to 38, or twice 19. * The
projective special linear group In mathematics, especially in the group theoretic area of algebra, the projective linear group (also known as the projective general linear group or PGL) is the induced action of the general linear group of a vector space ''V'' on the associat ...
L2(19) represents the abstract symmetry structure of the 57-cell: a unique or ''universal''
abstract polytope In mathematics, an abstract polytope is an algebraic partially ordered set which captures the dyadic property of a traditional polytope without specifying purely geometric properties such as points and lines. A geometric polytope is said to be ...
in the fourth dimension with a total of one hundred and seventy-one edges and vertices (
171 Year 171 ( CLXXI) was a common year starting on Monday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Severus and Herennianus (or, less frequently, year 924 '' Ab urbe co ...
= 19 x 9), and fifty-seven hemi-icosahedral cells that are self-dual. * There are nineteen
uniform honeycomb In geometry, a uniform honeycomb or uniform tessellation or infinite uniform polytope, is a vertex-transitive honeycomb made from uniform polytope facets. All of its vertices are identical and there is the same combination and arrangement of face ...
s from the _4
tesseractic honeycomb In four-dimensional euclidean geometry, the tesseractic honeycomb is one of the three regular space-filling tessellations (or honeycombs), represented by Schläfli symbol , and constructed by a 4-dimensional packing of tesseract facets. Its ver ...
in the 4-space, and nineteen
uniform polytope In geometry, a uniform polytope of dimension three or higher is a vertex-transitive polytope bounded by uniform facets. The uniform polytopes in two dimensions are the regular polygons (the definition is different in 2 dimensions to exclude vert ...
s with \mathrm A_ simplex symmetry exist in 5-space. There are infinitely many finite-volume Vinberg polytopes up through
dimension In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coor ...
nineteen. *''R''19 is the second base-10 repunit prime, short for the number 1111111111111111111. If the
Tits group In group theory, the Tits group 2''F''4(2)′, named for Jacques Tits (), is a finite simple group of order :   211 · 33 · 52 · 13 = 17,971,200. It is sometimes considered a 27th sporadic group ...
is included as a (nonstrict)
group of Lie type In mathematics, specifically in group theory, the phrase ''group of Lie type'' usually refers to finite groups that are closely related to the group of rational points of a reductive linear algebraic group with values in a finite field. The phra ...
, then there are 19 finite simple groups that are not
sporadic groups In mathematics, a sporadic group is one of the 26 exceptional groups found in the classification of finite simple groups. A simple group is a group ''G'' that does not have any normal subgroups except for the trivial group and ''G'' itself. Th ...
. In the Happy Family, 19 of 26 sporadic groups are subquotients of the Friendly Giant, which is also its own subquotient.


Science

* 19 is the
atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
of
potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...
. * 19 years is very close to 235
lunation In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Variations In Shona, Middle Eastern, and Euro ...
s. See
Metonic cycle The Metonic cycle or enneadecaeteris (from grc, ἐννεακαιδεκαετηρίς, from ἐννεακαίδεκα, "nineteen") is a period of almost exactly 19 years after which the lunar phases recur at the same time of the year. The rec ...
. *
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quickly ...
is the shortened name of Coronavirus disease 2019, the cause of the global pandemic that began in 2019. * The James Webb Space Telescope's optical elements are in an array of 19 hexagons, wherein 18 segmented primary mirrors focus light into a centered secondary mirror situated above the collecting mirrors, that in-turn reflects back onto the telescope's central imagers. It is a shape akin to the order-3 magic hexagon.


Religion


Islam

* The number of
angel In various theistic religious traditions an angel is a supernatural spiritual being who serves God. Abrahamic religions often depict angels as benevolent celestial intermediaries between God (or Heaven) and humanity. Other roles inclu ...
s guarding Hell ("Hellfire") ("Saqar") according to the
Qur'an The Quran (, ; Standard Arabic: , Quranic Arabic: , , 'the recitation'), also romanized Qur'an or Koran, is the central religious text of Islam, believed by Muslims to be a revelation from God. It is organized in 114 chapters (pl.: , s ...
: ''"Over it are nineteen"'' ( 74:30), after which the Qur'an describes this number as being ''"a trial for those who disbelieve"'' (74:31), a sign for people of the scripture to be ''"convinced"'' (74:31) and that believers ''"will increase in faith"'' (74:31) due to it. * The Number of Verse and Sura together in the Qur'an which announces Jesus son of Maryam's (Mary's) birth (Qur'an 19:19). * A group called United Submitter International claim the Quran has mathematical structure based on the number 19. The gematrical value of WAHD = 6+1+8+4=19, Wahd means 'One' (God) to the first verse (1:1), known as Bas-malah, consists of 19 Arabic letters or the Quran consists of 114 (19x6) surat etc.


Baháʼí faith

In the Bábí and
Baháʼí Faith The Baháʼí Faith is a religion founded in the 19th century that teaches the essential worth of all religions and the unity of all people. Established by Baháʼu'lláh in the 19th century, it initially developed in Iran and parts of the ...
s, a group of 19 is called a ''Váhid'', a Unity (
Arabic Arabic (, ' ; , ' or ) is a Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C. E.Watson; Walter ...
: واحد ''wāhid'', "one"). The numerical value of this word in the Abjad numeral system is 19. * The Baháʼí calendar is structured such that a year contains 19 months of 19 days each (along with the
intercalary Intercalation may refer to: *Intercalation (chemistry), insertion of a molecule (or ion) into layered solids such as graphite * Intercalation (timekeeping), insertion of a leap day, week or month into some calendar years to make the calendar foll ...
period of Ayyám-i-Há), as well as a 19-year cycle and a 361-year (19x19) supercycle. *The
Báb The Báb (b. ʿAlí Muḥammad; 20 October 1819 – 9 July 1850), was the messianic founder of Bábism, and one of the central figures of the Baháʼí Faith. He was a merchant from Shiraz in Qajar Iran who, in 1844 at the age of 25, claimed ...
and his disciples formed a group of 19. *There were 19
Apostles of Bahá'u'lláh An apostle (), in its literal sense, is an emissary, from Ancient Greek ἀπόστολος (''apóstolos''), literally "one who is sent off", from the verb ἀποστέλλειν (''apostéllein''), "to send off". The purpose of such sending ...
.


Celtic paganism

19 is a sacred number of the goddess
Brigid Brigid ( , ; meaning 'exalted one' from Old Irish),Campbell, MikBehind the Name.See also Xavier Delamarre, ''brigantion / brigant-'', in ''Dictionnaire de la langue gauloise'' (Éditions Errance, 2003) pp. 87–88: "Le nom de la sainte irlandais ...
because it is said to represent the 19-year cycle of the Great Celtic Year and the amount of time it takes the Moon to coincide with the winter solstice.Brigid: Triple Goddess of the Flame (Health, Hearth, & Forge)
/ref>


Music

*" 19" is a 1985 song by Paul Hardcastle, including
sampled Sample or samples may refer to: Base meaning * Sample (statistics), a subset of a population – complete data set * Sample (signal), a digital discrete sample of a continuous analog signal * Sample (material), a specimen or small quantity of so ...
soundbites taken from a documentary about the
Vietnam War The Vietnam War (also known by other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vietnam a ...
in which 19 is claimed to have been the average age of United States soldiers killed in the conflict. The song was parodied by British satirist
Rory Bremner Roderick Keith Ogilvy "Rory" Bremner,"Rory Bremner". '' Who Do You Think You Are?''. Wall to Wall for BBC One. 2 February 2009. No. 1, series 6. (born 6 April 1961) is a Scottish impressionist and comedian, noted for his work in political sati ...
under the pseudonym 'The Commentators,' as ''N-n-nineteen, Not Out'', the title referring to the batting average of David Gower, the
England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
cricket Cricket is a bat-and-ball game played between two teams of eleven players on a field at the centre of which is a pitch with a wicket at each end, each comprising two bails balanced on three stumps. The batting side scores runs by str ...
captain, during his side's risible performance against the
West Indies The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greate ...
in 1984 when they lost 5–0. *" I Was Only Nineteen" by the Australian group Redgum reached number one on the Australian charts in 1983. In 2005 a hip hop version of the song was produced by The Herd. *'' 19'' is the name of Adele's 2008 debut album, so named since she was 19 years old at the time. *"
Hey Nineteen "Hey Nineteen" is a song by the band Steely Dan from their album ''Gaucho'' (1980). Background According to one reviewer's interpretation, the song "was about a middle-aged man's disappointment with a young lover".Layman, Will"Jazz Today: The ...
" is a song by American jazz rock band Steely Dan, on the 1980 album ''Gaucho''. *Nineteen has been used as an alternative to twelve for a division of the octave into equal parts. This idea goes back to Salinas in the sixteenth century, and is interesting in part because it gives a system of
meantone Meantone temperament is a musical temperament, that is a tuning system, obtained by narrowing the fifths so that their ratio is slightly less than 3:2 (making them ''narrower'' than a perfect fifth), in order to push the thirds closer to pure. Me ...
tuning, being close to 1/3 comma meantone. ''See
19 equal temperament In music, 19 Tone Equal Temperament, called 19 TET, 19 EDO ("Equal Division of the Octave"), or 19  ET, is the tempered scale derived by dividing the octave into 19 equal steps (equal frequency ratios). Each step represent ...
.'' *Some organs use the 19th harmonic to approximate a minor third.


Literature

* Stephen King's eight-book epic ''The Dark Tower'' saga employs the number 19 in books '' The Dark Tower: The Gunslinger'', '' The Dark Tower V: Wolves of the Calla'', '' The Dark Tower VI: Song of Susannah'', '' The Dark Tower VII: The Dark Tower'', and ''
The Wind Through the Keyhole ''The Dark Tower: The Wind Through the Keyhole'' is a fantasy novel by American writer Stephen King. As part of ''The Dark Tower'' series, it is the eighth novel, but it is set chronologically between volumes four and five. First mentioned by Ki ...
'' as a mysterious and important number. They refer to the "ka-tet of 19", "Directive Nineteen," many names add up to 19, 19 seems to permeate every aspect of Roland and his traveler's lives. In addition, the number ends up being a powerful key. *In
Jodi Picoult Jodi Lynn Picoult () is an American writer. Picoult has published 28 novels, accompanying short stories, and has also written several issues of Wonder Woman. Approximately 40 million copies of her books are in print worldwide, translated into 34 ...
's bestselling book ''
Nineteen Minutes ''Nineteen Minutes'' (2007) is the fourteenth novel by the American author, Jodi Picoult. It was Picoult's first book to debut at #1 on the New York Times Best Seller list. This novel follows the unfolding of a school shooting, including the eve ...
'', the number 19 is referenced multiple times. It is most commonly referenced when referring to the main subject of the book, the
school shooting A school shooting is an attack at an educational institution, such as a primary school, secondary school, high school or university, involving the use of firearms. Many school shootings are also categorized as mass shootings due to multiple c ...
rampage that took place over a span of 19 minutes. *The novel '' S.'' by
Doug Dorst Doug Dorst is an American novelist, short story writer, and creative writing instructor. Dorst is a graduate of the Iowa Writers' Workshop and the Stegner Fellowship at Stanford University. He is the current director of the MFA Program in Creati ...
uses 19 and its multiples throughout. S is the 19th letter of the alphabet.


Games

*The game of Go is played on a grid of 19×19 lines (though variants can be played on grids of other sizes). *Though the maximum score for a
cribbage Cribbage, or crib, is a card game, traditionally for two players, that involves playing and grouping cards in combinations which gain points. It can be adapted for three or four players. Cribbage has several distinctive features: the cribbag ...
hand is 29, there is no combination of cards that adds up to 19 points. Many cribbage players, therefore, jokingly refer to a zero-point hand as "a 19 hand". *In the base version of ''
Settlers of Catan ''Catan'', previously known as ''The Settlers of Catan'' or simply ''Settlers'', is a multiplayer board game designed by Klaus Teuber. It was first published in 1995 in Germany by Franckh-Kosmos Verlag (Kosmos) as ''Die Siedler von Catan''. Pl ...
'' there are 19 hexagonal pieces that can be randomly or intentionally placed to form the board.


Age 19

*In four countries, 19 is the
age of majority The age of majority is the threshold of legal adulthood as recognized or declared in law. It is the moment when minors cease to be considered such and assume legal control over their persons, actions, and decisions, thus terminating the contr ...
. *In two countries, 19 is the minimum
legal drinking age The legal drinking age is the minimum age at which a person can legally consume alcoholic beverages. The minimum age alcohol can be legally consumed can be different from the age when it can be purchased in some countries. These laws vary between ...
. *In three countries, 19 is the minimum legal smoking age.


In sports

* In
golf Golf is a club-and-ball sport in which players use various clubs to hit balls into a series of holes on a course in as few strokes as possible. Golf, unlike most ball games, cannot and does not use a standardized playing area, and coping ...
, the '19th hole' is the clubhouse bar and in match play, if there is a tie after 18 holes, an extra hole(s) is played. In miniature golf it is an extra hole on which the winner earns an instant prize.


Other fields

* The
19th Amendment to the United States Constitution 19 (nineteen) is the natural number following 18 and preceding 20. It is a prime number. Mathematics 19 is the eighth prime number, and forms a sexy prime with 13, a twin prime with 17, and a cousin prime with 23. It is the third full re ...
gave American women the right to vote. * The
Vietnam War The Vietnam War (also known by other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vietnam a ...
spanned over 19 years, from November 1955 to April 1975.


References


External links


Number 19 at the Database of Number Correlations
{{DEFAULTSORT:19 (Number) Integers