general_fact: 21168 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 21168 is an uninteresting number.
trivia: 21168 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: December 14th is the day in 1958 that the 3rd Soviet Antarctic Expedition becomes the first expedition to reach The Pole of Relative Inaccessibility in the Antarctic.