69 (number)

This article is about the number. For the years, see 69 BC and AD 69. For other uses, see 69.

← 68 69 70 →
Cardinalsixty-nine
Ordinal69th
(sixty-ninth)
Factorization3 × 23
Divisors1, 3, 23, 69
Greek numeralΞΘ´
Roman numeralLXIX, lxix
Binary10001012
Ternary21203
Senary1536
Octal1058
Duodecimal5912
Hexadecimal4516
Chinese numeral,
Japanese numeral		六十九
ASCII valueE

69 (sixty-nine; LXIX) is the natural number following 68 and preceding 70. An odd number and a composite number, 69 is divisible by 1, 3, 23 and 69.

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 is a semiprime because it is a natural number that is the product of exactly two prime numbers (3 and 23), and it is an interprime between the numbers of 67 and 71.[1][2] 69 is not divisible by any square number other than 1, making it a square-free integer.[3] 69 is a Blum integer since the two factors of 69 are both Gaussian primes, and an Ulam number—an integer that is the sum of two distinct previously occurring Ulam numbers in a sequence.[a][4][6] 69 is a deficient number because the sum of its proper divisors (excluding itself) is less than the number of itself.[7] As an integer for which the arithmetic mean average of its positive divisors is also an integer, 69 is an arithmetic number.[8] 69 is a congruent number—a positive integer that is the area of a right triangle with three rational number sides—and an amenable number.[9][10] 69 can be expressed as the sum of consecutive positive integers in multiple ways, making it a polite number.[11] 69 is 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][13][14]

In decimal, 69 is the only natural number whose square (4761) and cube (328509) use every digit from 0–9 exactly once.[15][16] 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.[17] In its binary expansion of 1000101,[18] 69 is equal to 105 octal, while 105 is equal to 69 hexadecimal (this same property can be applied to all numbers from 64 to 69).[19][20] In computing, 69 equates to 2120 in ternary (base-3); 153 in senary (base-6); and 59 in duodecimal (base-12).[21][22][23]

Visually, in Arabic numerals, 69 is a strobogrammatic number because it looks the same when viewed both right-side and upside down.[24] 69 is a centered tetrahedral number, a figurate number that represents a pyramid with a triangular base and all other points arranged in layers above the base, forming a tetrahedron shape.[25] 69 is also a pernicious number because there is a prime number of 1s when it is written as a binary number, and an odious number as it is a positive integer that has an odd number of 1s in its binary expansion.[26][27]

In other fields

69ing is a sex position wherein each partner aligns themselves to simultaneously achieve oral sex with each other.[28] 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.[29] 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".[29] 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.[30]

See also

Explanatory footnotes

  1. ^ 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.[4][5]
  2. ^ 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.[12]

References

  1. ^ Neil, Sloane; Guy, R. K. (22 August 2010). "A001358: Semiprimes (or biprimes): products of two primes". On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 19 April 2019. Retrieved 22 April 2024.
  2. ^ Kimberling, Clark (n.d.). "A024675: Average of two consecutive odd primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 4 March 2024. Retrieved 22 April 2024.
  3. ^ Sloane, Neil (n.d.). "A005117: Squarefree numbers: numbers that are not divisible by a square greater than 1". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 27 May 2019. Retrieved 22 April 2024.
  4. ^ a b Gupta, 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. ISBN 9781599730882.
  5. ^ Recaman, Bernardo (1973). "Questions on a sequence of Ulam". American Mathematical Monthly. 80 (8). Mathematical Association of America: 919–920. doi:10.2307/2319404. JSTOR 2319404.
  6. ^ Wilson, Robert G. (n.d.). "A016105: Blum integers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 17 October 2018. Retrieved 22 April 2024.
  7. ^ Sloane, Neil; Steinerberger, Stefan (31 March 2006). "A005100: Deficient numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 22 March 2023. Retrieved 22 April 2024.
  8. ^ Sloane, Neil; Bernstein, Mira (3 April 2006). "A003601: Numbers j such that the average of the divisors of j is an integer: sigma_0(j) divides sigma_1(j). Alternatively, numbers j such that tau(j) (A000005(j)) divides sigma(j) (A000203(j))". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 26 March 2024. Retrieved 22 April 2024.
  9. ^ Alter, Ronald; Curtz, Thaddeus B. (January 1974). "A Note on Congruent Numbers". Mathematics of Computation. 28 (125). American Mathematical Society: 304–305. doi:10.2307/2005838. JSTOR 2005838.
  10. ^ Beedassy, Lekraj (7 January 2005). "A100832: Amenable numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 19 December 2023. Retrieved 22 April 2024.
  11. ^ Orlovsky, Vladimir Joseph Stephan; White, Carl R. (22 July 2009). "A138591: Sums of two or more consecutive nonnegative integers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 12 March 2019. Retrieved 22 April 2024.
  12. ^ Giblin, P[eter] J. (1993). Primes and Programming. Cambridge University Press. p. 67. ISBN 9780521409889.
  13. ^ Neil, Sloane (16 December 2010). "A002808: Composite numbers". On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 11 May 2024. Retrieved 22 April 2024.
  14. ^ Neil, Sloane (7 March 2008). "A000959: Lucky numbers". On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 19 April 2019. Retrieved 22 April 2024.
  15. ^ Wells, David (1997). The Penguin Dictionary of Curious and Interesting Numbers (2 ed.). Penguin Books. p. 100. ISBN 0-14-008029-5.
  16. ^ Barbeau, Edward (1997). Power Play. Mathematical Association of America. p. 126. ISBN 9780883855232.
  17. ^ Brannan, David Alexander (2006). A First Course in Mathematical Analysis. Cambridge University Press. p. 303. ISBN 9781139458955.
  18. ^ Konheim, Alan G. (2007). Computer Security and Cryptography. Wiley. p. 382. ISBN 9780470083970.
  19. ^ Topham, Douglas W. (2012). A System V Guide to UNIX and XENIX. Springer New York. p. 78. ISBN 9781461232469.
  20. ^ Holmay, Patrick (1998). "ASCII Character Set (Continued)". The OpenVMS User's Guide. Elsevier Science. p. 272. ISBN 9781555582036.
  21. ^ Clifford, Jerrold R.; Clifford, Martin (1974). Computer Mathematics Handbook. Allyn & Bacon. p. 276.
  22. ^ Scott, Norman Ross (1960). Analog and Digital Computer Technology. McGraw-Hill. p. 221.
  23. ^ Meyer, Jerome S. (1963). More Fun with Mathematics. Gramercy Publishing Company. p. 73.
  24. ^ Deza, Elena (2013). Perfect And Amicable Numbers. World Scientific. p. 390. ISBN 9789811259647.
  25. ^ Deza, Elena; Deza, Michel (2012). Figurative Numbers. World Scientific. pp. 126–127. ISBN 9789814355483.
  26. ^ Gow, Jeremy (8 February 2000). "A052294: Pernicious numbers: numbers with a prime number of 1's in their binary expansion". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 22 April 2024.
  27. ^ Sloane, Neil (n.d.). "A000069: Odious numbers: numbers with an odd number of 1's in their binary expansion". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 11 September 2018. Retrieved 22 April 2024.
  28. ^ Coleman, Julia (2022). Love, Sex, and Marriage: A Historical Thesaurus. Brill Publishers. p. 214. ISBN 9789004488502.
  29. ^ a b Feldman, Brian (9 June 2016). "Why 69 Is the Internet's Coolest Number (Sex)". Intelligencer. Archived from the original on 4 August 2022. Retrieved 22 April 2024.
  30. ^ Witt, Stephen (16 January 2019). "Tekashi 69: The Rise and Fall of a Hip-Hop Supervillain". Rolling Stone. Archived from the original on 1 June 2020. Retrieved 23 April 2024.