52 (number)

Template:Infobox 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 Template:Nobr where Template:Mvar is some prime larger than Template:Nobr It is the sixth of this form and the fifth of the form Template:Nobr
• the 5th Bell number,<ref>

{{#invoke:citation/CS1|citation |CitationClass=web }} </ref> the number of ways to partition a set of 5 objects.

• a decagonal number.<ref>

{{#invoke:citation/CS1|citation |CitationClass=web }} </ref>

• with an aliquot sum of 46; within an aliquot sequence of seven composite numbers Template:Math 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.<ref>

{{#invoke:citation/CS1|citation |CitationClass=web }} </ref>

• a noncototient since it is not equal to Template:Math for any Template:Nobr<ref>

{{#invoke:citation/CS1|citation |CitationClass=web }} </ref>

• a vertically symmetrical number.<ref>

{{#invoke:citation/CS1|citation |CitationClass=web }} </ref>

In other fields

File:Piano keyboard.JPG

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