Fait général: 6643 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 6643 is the smallest number which is palindromic in bases 2 and 3.
Culture générale: 6643 is an unremarkable number.
Date historique: March 9th is the day in 1841 that the U.S. Supreme Court rules that captive Africans who had seized control of the ship carrying them had been taken into slavery illegally.