Fait général: 21453 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 21453 is a boring number.
Culture générale: 21453 is an uninteresting number.
Date historique: September 25th is the day in 1690 that Publick Occurrences Both Foreign and Domestick, the first newspaper to appear in the Americas, is published for the first and only time.