Fait général: 21745 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 21745 is a boring number.
Culture générale: 21745 is an unremarkable number.
Date historique: July 14th is the day in 1916 that Start of the Battle of Delville Wood as an action within the Battle of the Somme, which was to last until 3 September 1916.