Fatto matematico: 6424 is the number of minimal covers of a set containing 6 elements.
Trivia: 6424 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: August 2nd is the day in 1869 that Japan's samurai, farmer, artisan, merchant class system (Shinōkōshō) is abolished as part of the Meiji Restoration reforms.