Fatto matematico: 6309 is the closest integer to 25^{e}.
Trivia: 6309 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: April 9th is the day in 475 that Byzantine Emperor Basiliscus issues a circular letter (Enkyklikon) to the bishops of his empire, supporting the Monophysite christological position.