Fatto generale: 1531 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 1531 is a boring number.
Trivia: 1531 is a boring number.
Data storica: March 10th is the day in 1891 that Almon Strowger, an undertaker in Topeka, Kansas, patents the Strowger switch, a device which led to the automation of telephone circuit switching.