Fatto generale: 6921 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 6921 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 6921 is a boring number.
Data storica: December 12th is the day in 1408 that the Order of the Dragon a monarchical chivalric order is created by Sigismund of Luxembourg, then King of Hungary.