Fatto generale: 9403 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 9403 is 65821 / 7, and each digit is contained in the equation exactly once.
Trivia: 9403 is an unremarkable number.
Data storica: September 28th is the day in 1912 that the Ulster Covenant is signed by half a million Ultonians in opposition to the Third Irish Home Rule Bill.