Fatto generale: 804 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 804 is a value of n for which 2f(n) = f(n+1).
Trivia: 804 is an uninteresting number.
Data storica: March 14th is the day in 1381 that Chioggia concludes an alliance with Zadar and Trogir against Venice, which becomes changed in 1412 in Šibenik.