general_fact: 20390 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 20390 is a boring number.
trivia: 20390 is an unremarkable number.
historical_date: October 28th is the day in 1929 that Black Monday, a day in the Wall Street Crash of 1929, which also saw major stock market upheaval.