39 (number)

"Thirty-nine" redirects here. For the South Korean drama series, see Thirty-Nine.

← 38 39 40 →
← 30 31 32 33 34 35 36 37 38 39 → List of numbers Integers ← 0 10 20 30 40 50 60 70 80 90 →
Cardinal	thirty-nine
Ordinal	39th (thirty-ninth)
Factorization	3 × 13
Divisors	1, 3, 13, 39
Greek numeral	ΛΘ´
Roman numeral	XXXIX, xxxix
Binary	1001112
Ternary	11103
Senary	1036
Octal	478
Duodecimal	3312
Hexadecimal	2716

39 (thirty-nine) is the natural number following 38 and preceding 40.

In mathematics

The F26A graph has 39 edges, all equivalent.

• 39 is the 12th distinct semiprime ^[1] and the 4th in the (3.q) family. ^[2] It is the last member of the third distinct semiprime pair (38,39).
• 39 has an aliquot sum of 17, which is a prime. 39 is the 4th member of the 17-aliquot tree within an aliquot sequence of one composite numbers (39,17,1,0) to the Prime in the 17-aliquot tree.
• It is a perfect totient number. ^[3]
• 39 is the sum of five consecutive primes (3 + 5 + 7 + 11 + 13) and also is the product of the first and the last of those consecutive primes. Among small semiprimes only three other integers (10, 155, and 371) share this attribute. 39 also is the sum of the first three powers of 3 (3¹ + 3² + 3³). Given 39, the Mertens function returns 0. ^[4]
• 39 is the smallest natural number which has three partitions into three parts which all give the same product when multiplied: {25, 8, 6}, {24, 10, 5}, {20, 15, 4}.

• 39 is a Perrin number, coming after 17, 22, 29 (it is the sum of the first two mentioned). ^[5]
• Since the greatest prime factor of 39² + 1 = 1522 is 761, which is more than 39 twice, 39 is a Størmer number. ^[6]
• The F26A graph is a symmetric graph with 39 edges.

In other fields

Arts and entertainment

• Japanese wordplay and slang:
  • Internet chat slang for "Thank You" when written with numbers: 3 (三, san) and 9 (九, kyū). ^[7]
  • 39 has been associted with the virtual singer Hatsune Miku.
    This comes from the fact that Japanese characters can have multiple readings.
    "San" (三, 3) can also be read as "mi" (三) ^[8] , and "kyuu" (九, 9) can also be read as "ku" (九) ^[9] . Thus, if using the alternative readings, 39 (三十九, sanjūkyū) can also be read as 39 (三九, miku). ^{[10] [11]}

History

• In Afghanistan, the number 39 is considered unlucky, due to the belief that it is associated with pimps. See Curse of 39. ^[12]

References

1. Sloane, N. J. A. (ed.). "SequenceA001358". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
2. Sloane, N. J. A. (ed.). "SequenceA001748". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
3. "Sloane's A082897 : Perfect totient numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
4. "Sloane's A028442 : Numbers n such that Mertens' function is zero". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
5. "Sloane's A001608 : Perrin sequence". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
6. "Sloane's A005528 : Størmer numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
7. Specktor, Brandon (2 November 2017). "Here's Why the Number "39" Means "Thank You" in Japan". Reader's Digest. Retrieved 23 March 2021.
8. "Definition of 三". jisho.org. Retrieved 24 March 2025.
9. "Definition of 九". jisho.org. Retrieved 24 March 2025.
10. "3/9 Marks Happy "Miku" & "Zaku" Day In Japan, Fan Artists Mark The Occasion". Crunchyroll. Retrieved 2024-08-15.
11. "What's up with Miku and 39?". gamespot.com. Retrieved 24 March 2025.
12. "Loya jirga: Afghan elders reject 'pimp's number 39'". BBC News. 17 November 2011. Retrieved 3 May 2012.