Fatto matematico: 21732 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 21732 is an unremarkable number.
Data storica: July 1st is the day in 1770 that Lexell's Comet passed closer to the Earth than any other comet in recorded history, approaching to a distance of 0.0146 a.u.