Mathematical fact: 7427 is the number of inequivalent asymmetric Ferrers graphs with 35 points.
Trivia: 7427 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Historical date: May 1st is the day in 880 that the Nea Ekklesia is inaugurated in Constantinople, setting the model for all later cross-in-square Orthodox churches.