Fatto generale: 21065 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21065 is a boring number.
Trivia: 21065 is an uninteresting number.
Data storica: September 2nd is the day in 1649 that the Italian city of Castro is completely destroyed by the forces of Pope Innocent X, ending the Wars of Castro.