Fait général: 21781 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 21781 is an uninteresting number.
Culture générale: 21781 is an uninteresting number.
Date historique: August 19th is the day in 2002 that a Russian Mi-26 helicopter carrying troops is hit by a Chechen missile outside of Grozny, killing 118 soldiers.