general_fact: 8573 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 8573 is an unremarkable number.
trivia: 8573 is an uninteresting number.
historical_date: June 21st is the day in 1900 that Baron Eduard Toll, leader of the Russian Polar Expedition of 1900, departed Saint Petersburg in Russia on the explorer ship Zarya, never to return.