Fatto generale: 21337 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21337 is a boring number.
Trivia: 21337 is an uninteresting number.
Data storica: June 1st is the day in 1779 that Benedict Arnold, a general in the Continental Army during the American Revolutionary War, is court-martialed for malfeasance.