Fifty-two is

• The approximate number of weeks in a year. 
• A significant number in the Maya calendar
• 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 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

Source: Wikipedia