math_fact: 810 is a value of n for which n-1 and n+1 are twin primes, and so are 2n-1 and 2n+1.
trivia: 810 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: March 20th is the day in 1964 that the precursor of the European Space Agency, ESRO (European Space Research Organization) is established per an agreement signed on June 14, 1962.