Fatto generale: 1257 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 1257 is a value of n for which f(s(n)) = f(n).
Trivia: 1257 is a boring number.
Data storica: June 10th is the day in 1918 that the Austro-Hungarian battleship SMS Szent István sinks after being torpedoed by an Italian MAS motorboat.