Fatto generale: 9913 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 9913 is an unremarkable number.
Trivia: 9913 is an uninteresting number.
Data storica: February 20th is the day in 1792 that the Postal Service Act, establishing the United States Post Office Department, is signed by President George Washington.