general_fact: 21909 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 21909 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
trivia: 21909 is an uninteresting number.
historical_date: December 25th is the day in 1974 that Marshall Fields drives a vehicle through the gates of the White House, resulting in a four-hour standoff.