Fait général: 5581 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 5581 is a boring number.
Culture générale: 5581 is a boring number.
Date historique: April 12th is the day in 1820 that Alexander Ypsilantis is declared leader of Filiki Eteria, a secret organization to overthrow Ottoman rule over Greece.