General fact: 21038 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 21038 is an uninteresting number.
Trivia: 21038 is an uninteresting number.
Historical date: August 6th is the day in 1988 that the Tompkins Square Park Police Riot in New York City spurs a reform of the NYPD, held responsible for the event.