general_fact: 21210 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 21210 is a boring number.
trivia: 21210 is a boring number.
historical_date: January 25th is the day in 2006 that Mexican professional wrestler Juana Barraza is arrested in conjunction with the serial killing of at least 10 elderly women.