Hecho general: 5257 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 5257 is a member of the Fibonacci-type sequence starting with 1 and 8.
Trivia: 5257 is a boring number.
Fecha histórica: May 23rd is the day in 1805 that Napoleon Bonaparte is crowned King of Italy with the Iron Crown of Lombardy in the Cathedral of Milan.