Fait général: 1421 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 1421 is a value of n for which s(f(n)) = 2s(n).
Culture générale: 1421 is a boring number.
Date historique: November 21st is the day in 1918 that Flag of Estonia, previously used by pro-independence activists, is formally adopted as national flag of the Republic of Estonia.