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 1971 that Typhoon Nancy, with possibly the strongest winds ever measured in a tropical cyclone, makes landfall in Osaka, Japan, killing 173 people.