Fait mathématique: 4478 is the number of fullerenes with 66 carbon atoms.
Culture générale: 4478 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: April 4th is the day in 1841 that William Henry Harrison dies of pneumonia becoming the first President of the United States to die in office and the one with the shortest term served.