Fatto generale: 9931 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 9931 is a boring number.
Trivia: 9931 is an uninteresting number.
Data storica: March 10th is the day in 2005 that Tung Chee Hwa resigns from his post as the first Chief Executive of Hong Kong after widespread public dissatisfaction of his tenure.