general_fact: 21778 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 21778 is an unremarkable number.
trivia: 21778 is an unremarkable number.
historical_date: August 16th is the day in 1920 that Ray Chapman of the Cleveland Indians is hit on the head by a fastball thrown by Carl Mays of the New York Yankees, and dies early the next day.