general_fact: 21499 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 21499 is an unremarkable number.
trivia: 21499 is an uninteresting number.
historical_date: November 10th is the day in 1958 that the Hope Diamond is donated to the Smithsonian Institution by New York diamond merchant Harry Winston.