Fatto generale: 784 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 784 is the sum of the first 7 cubes.
Trivia: 784 is an uninteresting number.
Data storica: February 22nd is the day in 1983 that the notorious Broadway flop Moose Murders opens and closes on the same night at the Eugene O'Neill Theatre.