Fait général: 13421 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 13421 is an unremarkable number.
Culture générale: 13421 is an uninteresting number.
Date historique: September 28th is the day in 1928 that Sir Alexander Fleming notices a bacteria-killing mold growing in his laboratory, discovering what later became known as penicillin.