general_fact: 15855 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 15855 is an unremarkable number.
trivia: 15855 is a boring number.
historical_date: May 29th is the day in 1953 that Edmund Hillary and Sherpa Tenzing Norgay become the first people to reach the summit of Mount Everest, on Tenzing Norgay's (adopted) 39th birthday.