Via Wikipedia 52 (fifty-two) is the natural number following 51 and preceding 53.

In mathematics
Fifty-two is the 5th Bell number and a decagonal number. 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 never the answer to the equation x - φ(x).

The piano has 52 white keys

Fifty-two is:
- The approximate number of weeks in a year. 52 weeks equal 364 days, while the tropical year is 365.24 days long. According to ISO 8601, most years have 52 weeks while some have 53.
- The number of countries in Africa
- The number of sons of Nebo in the Census of men of Israel upon return from exile (Holy Bible, Ezra 2:29)
- On the 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 Pick-up
- For over twenty years, this was the best-known car number of retired NASCAR driver Jimmy Means
- The code for international direct dial phone calls to Mexico
- A comic series from DC Comics entitled 52
- The number of letters in the English alphabet, if majuscules are distinguished from minuscules
- The number worn by Craig Rivet, Montreal Canadian defenseman (hockey), also known as “The Savior”