Fatto generale: 990 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 990 is a triangular number that is the product of 3 consecutive integers.
Trivia: 990 is an uninteresting number.
Data storica: September 16th is the day in 1701 that James Francis Edward Stuart, sometimes called the "Old Pretender", becomes the Jacobite claimant to the thrones of England and Scotland.