Fatto matematico: 8631 is a value of n for which 3n and 7n together use each digit exactly once.
Trivia: 8631 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: August 18th is the day in 1920 that the Nineteenth Amendment to the United States Constitution is ratified, guaranteeing women's suffrage.