52 (fifty-two) is the natural number following 51 and preceding 53.
In mathematics
Fifty-two is
- a composite number; a square-prime, of the form where is some prime larger than It is the sixth of this form and the fifth of the form
- the 5th Bell number, the number of ways to partition a set of 5 objects.
- a decagonal number.
- with an aliquot sum of 46; within an aliquot sequence of seven composite numbers to the prime in the 3-aliquot tree. This sequence does not extend above 52 because it is,
- an untouchable number, since it is never the sum of proper divisors of any number. It is the first untouchable number larger than 2 and 5.
- a noncototient since it is not equal to for any
- a vertically symmetrical number, (as on calculator displays).
In other fields
thumb|120px|A full-size [[piano has 52 white keys, out of 88 total keys.]]
Fifty-two is:
- The number of cards in a standard deck of playing cards, not counting Jokers or advertisement cards
- The number of weeks in a calendar year
- The number of white keys on a piano
- The number of explicit bits used to store the significand in an IEEE 754 double