Fait mathématique: 13781 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Culture générale: 13781 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: September 23rd is the day in 1905 that Norway and Sweden sign the "Karlstad treaty", peacefully dissolving the Union between the two countries.