Fatto generale: 635 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 635 is a number n whose 5^{th} root has a decimal part that begins with the digits of n.
Trivia: 635 is an uninteresting number.
Data storica: September 26th is the day in 1212 that Golden Bull of Sicily is certified as an hereditary royal title in Bohemia for the Přemyslid dynasty.