Fatto generale: 552 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 552 is the number of prime knots with 11 crossings.
Trivia: 552 is a boring number.
Data storica: July 5th is the day in 1935 that the National Labor Relations Act, which governs labor relations in the United States, is signed into law by President Franklin D. Roosevelt.