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 uninteresting number.
Data storica: September 28th is the day in 1787 that the newly completed United States Constitution is voted on by the U.S. Congress to be sent to the state legislatures for approval.