Fatto generale: 21800 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21800 is an unremarkable number.
Trivia: 21800 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: September 7th is the day in 1906 that Alberto Santos-Dumont flies his 14-bis aircraft at Bagatelle, France for the first time successfully.