Fait mathématique: 6821 is an unremarkable number.
Culture générale: 6821 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: September 3rd is the day in 1999 that an 87-automobile pile-up happens on Highway 401 freeway just East of Windsor, Ontario, Canada after an unusually thick fog from Lake St. Clair.