The number and its pictograph give its name to the
sexual position of
the same name. The association of the number with this sex position has resulted in it being associated in meme culture with sex. People knowledgeable of the meme may respond "nice" in response to the appearance of the number, whether intentionally an innuendo or not.
In mathematics
69, spelled sixty-nine and known in
Roman numerals as LXIX,[a] is the
natural number that follows
68 and precedes
70.[1][2] An
odd number, 69 is
divisible by
1,
3,
23 and 69.[3][4] 69 is a
composite number, meaning that it is not a
prime, and a
lucky number because it is a natural number that remains after repeatedly removing every nth number in a sequence of natural numbers, starting from 1.[b][6][7] As a natural number that is the
product of exactly two prime numbers (a
factorisation of 3 x 23), 69 is a
semiprime and an
interprime between the prime numbers of
67 and
71.[8][9] The
aliquot sum—the
total sum of all the divisors of a number, excluding the number itself—of 69 is
27 within the
aliquot sequence of numbers where each number is the aliquot sum of the previous number (69, 27,
13, 1,
0). 69 is the third composite number in the 13-aliquot tree, following 27 and
35.[10]
In
decimal, 69 is the only natural number whose
square (4761) and
cube (328509) use every digit from 0–9 exactly once.[20][21] It is also the largest number whose
factorial is less than a
googol. On many handheld scientific and graphing
calculators, 69! (1.711224524×1098) is the highest factorial that can be calculated due to memory limitations.[22] In its
binary expansion of 1000101,[23] 69 is equal to
105octal, while 105 is equal to 69
hexadecimal (this same property can be applied to all numbers from
64 to 69).[24][25] In
computing, 69 equates to 2120 in
ternary (base-3); 153 in
senary (base-6); and 59 in
duodecimal (base-12).[26][27][28]
69ing is a
sex position wherein each partner aligns themselves to simultaneously achieve
oral sex with each other.[38] In reference to this sex act, the number 69 itself has become an
Internet meme as an inherently funny number in which users will respond to any occurrence of the number with the word "nice" to draw specific attention to it.[39] This means to humorously imply that the reference to the sex position was intentional. Because of its association with the sex position and resulting meme, 69 has been named "the sex number".[39] In music, the American rapper
6ix9ine (pronounced "six nine") chose the stage name in reference to the sex position as well as the
yin-yang symbol.[40]
^Where n is the next number in the list after the last surviving number; every second number (all
even numbers) in the list of numbers (1 through
infinity) is eliminated first (1, 3, 5, 7, 9, 11 …), every third number (1, 3, 7, 9 …), then every seventh number, and so forth.[5]
^As a consequence of the definition of the Ulam sequence, 3 is an Ulam number (1 + 2) and 4 is an Ulam number (1 + 3 ). 5 is not an Ulam number, because 5 = 1 + 4 = 2 + 3. 69 is an Ulam number as the sum of 16 + 53; both 16 and 53 are Ulam numbers.[12][13]
^
abGupta, Shyam Sunder (2009). "Smarandache sequence of Ulam numbers". In Wenpeng, Zhang (ed.). Research on Number Theory and Smarandache Notions: Proceedings of the Fifth International Conference on Number Theory and Smarandache Notions. Hexis. p. 78.
ISBN9781599730882.
^Wilson, Robert G. (n.d.).
"A016105: Blum integers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 22 April 2024.
^Sloane, Neil; Steinerberger, Stefan (31 March 2006).
"A005100: Deficient numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 22 April 2024.
^Beedassy, Lekraj (7 January 2005).
"A100832: Amenable numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 22 April 2024.
^Steinicke, Wolfgang (2010). Observing and Cataloguing Nebulae and Star Clusters: From Herschel to Dreyer's New General Catalogue.
Cambridge University Press. p. 191.
ISBN9781139490108.