52 (number)

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 (p2, q) where q is a higher prime. It is the sixth of this form and the fifth of the form (22.q).
 * 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 (52,46,26,16,15, 9,4,3,1,0) 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, and it is a noncototient since it is not equal to x − φ(x) for any x.
 * a vertically symmetrical number.

In science

 * The atomic number of tellurium

Astronomy

 * Messier object M52, a magnitude 8.0 open cluster in the constellation Cassiopeia, also known as NGC 7654.
 * The New General Catalogue object NGC 52, a spiral galaxy in the constellation Pegasus.

In other fields
Fifty-two is:
 * The approximate number of weeks in a year. 52 weeks is 364 days, while the tropical year is 365.24 days long. According to ISO 8601, most years have 52 weeks while some have 53.
 * A significant number in the Maya calendar
 * On the modern piano, the number of white keys (notes in the C major scale)
 * The number of cards in a standard deck of playing cards, not counting Jokers or advertisement cards
 * The name of a practical joke card game 52 Pickup
 * 52 Pick-Up is a film starring Roy Scheider and Ann Margaret
 * The code for international direct dial phone calls to Mexico
 * A weekly comic series from DC Comics entitled 52 has 52 issues, with a plot spanning one full year.
 * The New 52 is a 2011 revamp and relaunch by DC Comics of its entire line of ongoing monthly superhero books.
 * The number of letters in the English alphabet, if majuscules are distinguished from minuscules
 * The number of the French department Haute-Marne
 * 52nd Street (disambiguation)
 * 52 Hand Blocks, a variant of the martial art jailhouse rock.
 * 52 is the car number of retired NASCAR driver Jimmy Means
 * 52 American hostages were held in the Iran hostage crisis
 * The number of the laps of the British Grand Prix since 2010.

Historical years
52 BC, AD 52, 1052, 1952 etc.