69 (sixty-nine) 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 n ...

following 68 and preceding 70.

In mathematics

69 is: * a

lucky number In number theory, a lucky number is a natural number in a set which is generated by a certain "sieve". This sieve is similar to the Sieve of Eratosthenes that generates the primes, but it eliminates numbers based on their position in the remain ...

. * a

semiprime In mathematics, a semiprime is a natural number that is the product of exactly two prime numbers. The two primes in the product may equal each other, so the semiprimes include the squares of prime numbers. Because there are infinitely many prime nu ...

. * a

Blum integer In mathematics, a natural number ''n'' is a Blum integer if is a semiprime for which ''p'' and ''q'' are distinct prime numbers congruent to 3 mod 4.Joe Hurd, Blum Integers (1997), retrieved 17 Jan, 2011 from http://www.gilith.com/research/tal ...

, since the two factors of 69 are both

Gaussian prime In number theory, a Gaussian integer is a complex number whose real and imaginary parts are both integers. The Gaussian integers, with ordinary addition and multiplication of complex numbers, form an integral domain, usually written as \mathbf /ma ...

s. * the sum of the sums of the divisors of the first 9

positive integers 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 n ...

. * the third

composite number A composite number is a positive integer that can be formed by multiplying two smaller positive integers. Equivalently, it is a positive integer that has at least one divisor other than 1 and itself. Every positive integer is composite, prime, ...

in the 13-aliquot tree. The

aliquot sum In number theory, the aliquot sum ''s''(''n'') of a positive integer ''n'' is the sum of all proper divisors of ''n'', that is, all divisors of ''n'' other than ''n'' itself. That is, :s(n)=\sum\nolimits_d. It can be used to characterize the prime ...

of sixty-nine is 27 within the aliquot sequence (69,27,13,1,0). * a strobogrammatic number. * a

centered tetrahedral number A centered tetrahedral number is a centered figurate number that represents a tetrahedron In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, ...

. Because 69 has an odd number of 1s in its binary representation, it is sometimes called an "

odious number In number theory, an odious number is a positive integer that has an odd number of 1s in its binary expansion. In computer science, an odious number is said to have odd parity. Examples The first odious numbers are: Properties If a(n) denotes ...

." 69 is the only number whose square () and cube () use every decimal digit from 0–9 exactly once.David Wells: ''The Penguin Dictionary of Curious and Interesting Numbers'' 69 is equal to 105

octal The octal numeral system, or oct for short, is the radix, base-8 number system, and uses the Numerical digit, digits 0 to 7. This is to say that 10octal represents eight and 100octal represents sixty-four. However, English, like most languages, ...

, while 105 is equal to 69

hexadecimal In mathematics and computing, the hexadecimal (also base-16 or simply hex) numeral system is a positional numeral system that represents numbers using a radix (base) of 16. Unlike the decimal system representing numbers using 10 symbols, hexa ...

. This same property can be applied to all numbers from 64 to 69. On many handheld scientific and graphing

calculator An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics. The first solid-state electronic calculator was created in the early 1960s. Pocket-sized ...

s, the highest

factorial In mathematics, the factorial of a non-negative denoted is the product of all positive integers less than or equal The factorial also equals the product of n with the next smaller factorial: \begin n! &= n \times (n-1) \times (n-2) \t ...

that can be calculated, due to memory limitations, is 69! or about 1.711224524.

In science

* 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 ...

thulium Thulium is a chemical element with the symbol Tm and atomic number 69. It is the thirteenth and third-last element in the lanthanide series. Like the other lanthanides, the most common oxidation state is +3, seen in its oxide, halides and other c ...

, a

lanthanide The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...

Astronomy

* The

Messier object The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only int ...

M69 is a

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

9.0

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Sagittarius.

In other fields

Sixty-nine may also refer to: * 69ing, a sex position involving each partner aligning themselves to achieve oral sex simultaneously with each other. ** In reference to the sex position, "69" has become an

internet meme An Internet meme, commonly known simply as a meme ( ), is an idea, behavior, style, or image that is spread via the Internet, often through social media platforms. What is considered a meme may vary across different communities on the Internet ...

, where users will respond to any occurrence of the number with the word "nice" and draw specific attention to it. This means to sarcastically imply that the reference to the sex position was intentional. Because of its association with the sex position and resulting meme, "69" has become known as "the sex number". * The registry of the

U.S. Navy's The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the worl ...

aircraft carrier , named after Dwight D. Eisenhower, the 34th President of the United States and five-star general in the United States Army. * The number of the French department

Rhône The Rhône ( , ; wae, Rotten ; frp, Rôno ; oc, Ròse ) is a major river in France and Switzerland, rising in the Alps and flowing west and south through Lake Geneva and southeastern France before discharging into the Mediterranean Sea. At Ar ...

. The

Lyon Metropolis The Metropolis of Lyon (french: Métropole de Lyon), also known as ("Greater Lyon"), is a French territorial collectivity located in the east-central region of Auvergne-Rhône-Alpes. It is a directly elected metropolitan authority encompassing t ...

, which was separated from the Rhône department in 2015, is designated as "69M". The

postal codes A postal code (also known locally in various English-speaking countries throughout the world as a postcode, post code, PIN or ZIP Code) is a series of letters or digits or both, sometimes including spaces or punctuation, included in a postal a ...

for both entities start with "69". * The

Taijitu In Chinese philosophy, a ''taijitu'' () is a symbol or diagram () representing Taiji () in both its monist ('' wuji'') and its dualist (yin and yang) aspects. Such a diagram was first introduced by Neo-Confucian philosopher Zhou Dunyi (; 1 ...

* The last possible

television channel A television channel is a terrestrial frequency or virtual number over which a television station or television network is distributed. For example, in North America, "channel 2" refers to the terrestrial or cable band of 54 to 60 MHz, with ...

number in the UHF bandplan for American terrestrial television from 1982 until its withdrawal on December 31, 2011.

References

External links

* {{DEFAULTSORT:69 (Number) Integers Internet memes