general_fact: 21287 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 21287 is an unremarkable number.
trivia: 21287 is an unremarkable number.
historical_date: April 12th is the day in 1820 that Alexander Ypsilantis is declared leader of Filiki Eteria, a secret organization to overthrow Ottoman rule over Greece.