Fatto generale: 1517 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 1517 is the product of two consecutive primes.
Trivia: 1517 is a boring number.
Data storica: February 25th is the day in 1948 that the Communist Party takes control of government in Czechoslovakia and the period of the Third Republic ends.