general_fact: 42504 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 42504 is an unremarkable number.
trivia: 42504 is an uninteresting number.
historical_date: May 15th is the day in 1793 that Diego Marín Aguilera flies a glider for "about 360 meters", at a height of 5-6 meters, during one of the first attempted .