Fait mathématique: 5863 is the starting location of 7777 in the decimal expansion of p.
Culture générale: 5863 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: January 19th is the day in 379 that Emperor Gratian elevates Flavius Theodosius at Sirmium to Augustus, and gives him power over all the eastern provinces of the Roman Empire.