Fatto generale: 1131 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 1131 is an uninteresting number.
Trivia: 1131 is an unremarkable number.
Data storica: February 4th is the day in 960 that the coronation of Zhao Kuangyin as Emperor Taizu of Song, initiating the Song Dynasty period of China that would last more than three centuries.