general_fact: 4503 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 4503 is the largest number that is not the sum of 4 or fewer squares of composites.
trivia: 4503 is an uninteresting number.
historical_date: April 29th is the day in 1882 that the "Elektromote" – forerunner of the trolleybus – is tested by Ernst Werner von Siemens in Berlin.