39 (thirty-nine) is the

natural number In mathematics, the natural numbers are the numbers 0, 1, 2, 3, and so on, possibly excluding 0. Some start counting with 0, defining the natural numbers as the non-negative integers , while others start with 1, defining them as the positive in ...

following 38 and preceding 40.

In mathematics

*39 is the 12th distinct semiprime and the 4th in the (3.q) family. It is the last member of the third distinct semiprime pair ( 38,39). *39 has an

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

of 17, which is a prime. 39 is the 4th member of the 17-aliquot tree within an

aliquot sequence In mathematics, an aliquot sequence is a sequence of positive integers in which each term is the sum of the proper divisors of the previous term. If the sequence reaches the number 1, it ends, since the sum of the proper divisors of 1 is 0. Def ...

of one composite numbers (39, 17, 1,0) to the Prime in the 17-aliquot tree. *It is a perfect totient number. *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 (3 + 3 + 3). Given 39, the Mertens function returns 0. *39 is the smallest natural number which has three partitions into three parts which all give the same product when multiplied: , , . *39 is a Perrin number, coming after 17, 22, 29 (it is the sum of the first two mentioned). *Since the greatest prime factor of 39² + 1 = 1522 is 761, which is more than 39 twice, 39 is a Størmer number. *The F26A graph is a symmetric graph with 39 edges.

In other fields

Arts and entertainment

* Japanese wordplay and slang: **Through numeric substitution, 39 is the Internet chat slang term for "Thank you" when written with numbers: and . **39 has also been associated with the virtual singer Hatsune Miku for the same reason: can also be read as , and can also be read as . Thus, if using the alternative readings, can also be read as .

History

*In

Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan, is a landlocked country located at the crossroads of Central Asia and South Asia. It is bordered by Pakistan to the Durand Line, east and south, Iran to the Afghanistan–Iran borde ...

, the number 39 is considered unlucky, due to the belief that it is associated with

pimp Procuring, pimping, or pandering is the facilitation or provision of a prostitute or other sex worker in the arrangement of a sex act with a customer. A procurer, colloquially called a pimp (if male) or a madam (if female, though the term "pimp" ...

s. See Curse of 39.

References

{{Integers, zero Integers