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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 reptend prime In number theory, a full reptend prime, full repetend prime, proper primeDickson, Leonard E., 1952, ''History of the Theory of Numbers, Volume 1'', Chelsea Public. Co. or long prime in base ''b'' is an odd prime number ''p'' such that the Fermat q ...
, the fifth
central trinomial coefficient The trinomial triangle is a variation of Pascal's triangle. The difference between the two is that an entry in the trinomial triangle is the sum of the ''three'' (rather than the ''two'' in Pascal's triangle) entries above it: \begin & & & & 1\ ...
, and the seventh Mersenne prime exponent. It is also the second Keith number, 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, 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 In number theory, a Heegner number (as termed by Conway and Guy) is a square-free positive integer ''d'' such that the imaginary quadratic field \Q\left sqrt\right/math> has class number 1. Equivalently, its ring of integers has unique factoriza ...
. 67 and 163, respectively the 19th and 38th prime numbers, are the two largest Heegner numbers, of nine total. * 19 is the third centered triangular number as well as the third
centered hexagonal number In mathematics and combinatorics, a centered hexagonal number, or hex number, is a centered figurate number that represents a hexagon with a dot in the center and all other dots surrounding the center dot in a hexagonal lattice. The following ...
. : The 19th triangular number 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 integers, that is also the sixth
centered nonagonal number A centered nonagonal number (or centered enneagonal number) is a centered figurate number that represents a nonagon with a dot in the center and all other dots surrounding the center dot in successive nonagonal layers. The centered nonagonal n ...
. :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
109 109 may refer to: * 109 (number), the integer following 108 and preceding 110 * AD 109, a year of the Julian calendar, in the second century AD * 109 BC, a year of the pre-Julian Roman calendar * 109 (department store), a department store in Shib ...
, 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 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 zeros 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, as its reverse ( 91) is composite. 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 Hanover ...
, the first Hardy-Ramanujan number or taxicab number, also a
Harshad number In mathematics, a harshad number (or Niven number) in a given number base is an integer that is divisible by the sum of its digits when written in that base. Harshad numbers in base are also known as -harshad (or -Niven) numbers. Harshad numbers ...
, as it's divisible by the sum of its digits, 19. 91 is also the fourth
centered nonagonal number A centered nonagonal number (or centered enneagonal number) is a centered figurate number that represents a nonagon with a dot in the center and all other dots surrounding the center dot in successive nonagonal layers. The centered nonagonal n ...
. * 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 L2(19) represents the abstract symmetry structure of the 57-cell: a unique or ''universal'' abstract polytope in the fourth dimension with a total of one hundred and seventy-one
edges Edge or EDGE may refer to: Technology Computing * Edge computing, a network load-balancing system * Edge device, an entry point to a computer network * Adobe Edge, a graphical development application * Microsoft Edge, a web browser developed by ...
and vertices (
171 Year 171 (Roman numerals, 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 92 ...
= 19 x 9), and fifty-seven hemi-icosahedral cells that are
self-dual In mathematics, a duality translates concepts, theorems or mathematical structures into other concepts, theorems or structures, in a Injective function, one-to-one fashion, often (but not always) by means of an Involution (mathematics), involutio ...
. * There are nineteen uniform honeycombs from the _4 tesseractic honeycomb in the
4-space A four-dimensional space (4D) is a mathematical extension of the concept of three-dimensional or 3D space. Three-dimensional space is the simplest possible abstraction of the observation that one only needs three numbers, called ''dimensions'', ...
, and nineteen uniform polytopes with \mathrm A_
simplex In geometry, a simplex (plural: simplexes or simplices) is a generalization of the notion of a triangle or tetrahedron to arbitrary dimensions. The simplex is so-named because it represents the simplest possible polytope in any given dimension. ...
symmetry exist in 5-space. There are infinitely many finite-volume Vinberg polytopes up through dimension nineteen. *''R''19 is the second base-10
repunit prime In recreational mathematics, a repunit is a number like 11, 111, or 1111 that contains only the digit 1 — a more specific type of repdigit. The term stands for repeated unit and was coined in 1966 by Albert H. Beiler in his book ''Recreat ...
, short for the number 1111111111111111111. If the Tits group is included as a (nonstrict) group of Lie type, then there are 19 finite simple groups that are not sporadic groups. In the Happy Family, 19 of 26 sporadic groups are
subquotient In the mathematical fields of category theory and abstract algebra, a subquotient is a quotient object of a subobject. Subquotients are particularly important in abelian categories, and in group theory, where they are also known as sections, thou ...
s of the
Friendly Giant ''The Friendly Giant'' was a children's television program that aired on CBC Television from September 30, 1958 through to March 1985. It featured three main characters: a giant named Friendly (played by Bob Homme), who lived in a huge castle, alo ...
, which is also its own subquotient.


Science

* 19 is the atomic number of potassium. * 19 years is very close to 235 lunations. See Metonic cycle. * COVID-19 is the shortened name of
Coronavirus disease 2019 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 ...
, the cause of the
global pandemic Global means of or referring to a globe and may also refer to: Entertainment * Global (Paul van Dyk album), ''Global'' (Paul van Dyk album), 2003 * Global (Bunji Garlin album), ''Global'' (Bunji Garlin album), 2007 * Global (Humanoid album), ''Gl ...
that began in 2019. * The
James Webb Space Telescope The James Webb Space Telescope (JWST) is a space telescope which conducts infrared astronomy. As the largest optical telescope in space, its high resolution and sensitivity allow it to view objects too old, distant, or faint for the Hubble Spa ...
'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 angels guarding
Hell In religion and folklore, hell is a location in the afterlife in which evil souls are subjected to punitive suffering, most often through torture, as eternal punishment after death. Religions with a linear divine history often depict hell ...
("Hellfire") ("Saqar") according to the Qur'an: ''"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 Faiths, a group of 19 is called a ''Váhid'', a Unity ( Arabic: واحد ''wāhid'', "one"). The numerical value of this word in the Abjad numeral system is 19. * The
Baháʼí calendar The Badíʻ calendar used in the Baháʼí Faith is a solar calendar consisting of nineteen months and four or five intercalary days, with new year at the moment of Northern spring equinox. Each month is named after a virtue(e.g. Perfection, Mercy ...
is structured such that a year contains 19 months of 19 days each (along with the intercalary period of
Ayyám-i-Há Ayyám-i-Há is a period of intercalary days in the Baháʼí calendar, when Baháʼís celebrate the Festival of Ayyám-i-Há. The four or five days of this period are inserted between the last two months of the calendar (Mulk and ʻAláʼ). ...
), as well as a 19-year cycle and a 361-year (19x19) supercycle. *The Báb and his
disciples A disciple is a follower and student of a mentor, teacher, or other figure. It can refer to: Religion * Disciple (Christianity), a student of Jesus Christ * Twelve Apostles of Jesus, sometimes called the Twelve Disciples * Seventy disciples in ...
formed a group of 19. *There were 19 Apostles of Bahá'u'lláh.


Celtic paganism

19 is a sacred number of the goddess Brigid 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 soundbites taken from a documentary about the Vietnam War 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 under the pseudonym 'The Commentators,' as ''N-n-nineteen, Not Out'', the title referring to the batting average of David Gower, the England
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 striki ...
captain, during his side's risible performance against the West Indies 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" 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 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 Stephen Edwin King (born September 21, 1947) is an American author of horror, supernatural fiction, suspense, crime, science-fiction, and fantasy novels. Described as the "King of Horror", a play on his surname and a reference to his high s ...
'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'' 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's bestselling book '' Nineteen Minutes'', the number 19 is referenced multiple times. It is most commonly referenced when referring to the main subject of the book, the school shooting rampage that took place over a span of 19 minutes. *The novel '' S.'' by Doug Dorst 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 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'' 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. *In two countries, 19 is the minimum legal drinking age. *In three countries, 19 is the minimum
legal smoking age The smoking age is the minimum legal age required to purchase or use tobacco products. Most countries have laws that forbid sale of tobacco products to persons younger than certain ages, usually the age of majority. This article does not discus ...
.


In sports

* In golf, 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 Miniature golf, also known as minigolf, mini-putt, crazy golf, or putt-putt, is an offshoot of the sport of golf focusing solely on the putting aspect of its parent game. The aim of the game is to score the lowest number of points. It is played ...
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 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