Fatto generale: 4231 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 4231 is the number of labeled partially ordered sets with 5 elements.
Trivia: 4231 is an uninteresting number.
Data storica: August 1st is the day in 1980 that Vigdís Finnbogadóttir is elected President of Iceland and becomes the country's first democratically elected female head of state.