Fatto generale: 21683 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21683 is an uninteresting number.
Trivia: 21683 is a boring number.
Data storica: May 13th is the day in 1515 that Mary Tudor, Queen of France and Charles Brandon, 1st Duke of Suffolk are officially married at Greenwich.