Fatto generale: 21746 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21746 is an unremarkable number.
Trivia: 21746 is an uninteresting number.
Data storica: July 15th is the day in 1789 that Gilbert du Motier, marquis de La Fayette, is named by acclamation colonel-general of the new National Guard of Paris.