Fait général: 6424 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 6424 is the number of minimal covers of a set containing 6 elements.
Culture générale: 6424 is a boring number.
Date historique: August 2nd is the day in 1939 that Albert Einstein and Leó Szilárd write a letter to Franklin D. Roosevelt, urging him to begin the Manhattan project to develop a nuclear weapon.