General fact: 18900 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 18900 is an unremarkable number.
Trivia: 18900 is an uninteresting number.
Historical date: September 29th is the day in 522 BC that Darius I of Persia kills the Magian usurper Gaumâta, securing his hold as king of the Persian Empire.