Fait mathématique: 4527 is a value of n for which n and 7n together use each digit 1-9 exactly once.
Culture générale: 4527 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: 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.