Fait mathématique: 6345 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Culture générale: 6345 is an unremarkable number.
Date historique: May 15th is the day in 1252 that Pope Innocent IV issues the papal bull ad exstirpanda, which authorizes, but also limits, the torture of heretics in the Medieval Inquisition.