General fact: 1804 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 1804 is the number of 3×3 sliding puzzle positions that require exactly 14 moves to solve starting with the hole on a side.
Trivia: 1804 is an uninteresting number.
Historical date: December 8th is the day in 1987 that Frank Vitkovic shoots and kills eight people at the Australia Post building in Melbourne, before jumping to his death.