general_fact: 1421 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 1421 is a value of n for which s(f(n)) = 2s(n).
trivia: 1421 is a boring number.
historical_date: November 21st is the day in 2002 that NATO invites Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia to become members.