Fatto generale: 43131 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 43131 is an unremarkable number.
Trivia: 43131 is an unremarkable number.
Data storica: February 1st is the day in 1946 that the Parliament of Hungary abolishes the monarchy after nine centuries, and proclaims the Hungarian Republic.