Fait mathématique: 2557 is the number of proper divisors of the 15^{th} perfect number.
Culture générale: 2557 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: December 31st is the day in 1999 that the United States Government hands control of the Panama Canal (as well all the adjacent land to the canal known as the Panama Canal Zone) to Panama.