Fait général: 21815 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 21815 is a boring number.
Culture générale: 21815 is a boring number.
Date historique: September 22nd is the day in 1993 that a barge strikes a railroad bridge near Mobile, Alabama, causing the deadliest train wreck in Amtrak history.