Fatto generale: 21169 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21169 is an unremarkable number.
Trivia: 21169 is an uninteresting number.
Data storica: December 15th is the day in 1467 that Stephen III of Moldavia defeats Matthias Corvinus of Hungary, with the latter being injured thrice, at the Battle of Baia.