Fatto generale: 4217 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 4217 is the smallest number whose 8^{th} power has 29 digits.
Trivia: 4217 is an unremarkable number.
Data storica: July 18th is the day in 1555 that the College of Arms was reincorporated by Royal Charter signed by Queen Mary I of England and King Philip II of Spain.