Fatto matematico: 477 is the smallest number whose cube contains four 3's.
Trivia: 477 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: April 21st is the day in 1863 that Bahá'u'lláh, the founder of the Bahá'í Faith, declares his mission as "He whom God shall make manifest".