Fatto generale: 9980 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 9980 is an uninteresting number.
Trivia: 9980 is an unremarkable number.
Data storica: April 28th is the day in 1975 that General Cao Van Vien, chief of the South Vietnamese military, departs for the US as the North Vietnamese Army closed in on victory.