Fatto generale: 21579 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21579 is an uninteresting number.
Trivia: 21579 is an unremarkable number.
Data storica: January 29th is the day in 1979 that Brenda Spencer kills two people and wounds eight at the Grover Cleveland Elementary School shootings.