general_fact: 19604 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 19604 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
trivia: 19604 is an uninteresting number.
historical_date: September 2nd is the day in 1649 that the Italian city of Castro is completely destroyed by the forces of Pope Innocent X, ending the Wars of Castro.