Fatto generale: 522 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 522 is the number of ways to place a non-attacking white and black pawn on a 6×6 chessboard.
Trivia: 522 is an uninteresting number.
Data storica: June 5th is the day in 1975 that the United Kingdom holds its first country-wide referendum, on remaining in the European Economic Community (EEC).