Fatto matematico: 1640 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 1640 is an uninteresting number.
Data storica: June 27th is the day in 1844 that Joseph Smith, Jr., founder of the Latter Day Saint movement, and his brother Hyrum Smith, are murdered by a mob at the Carthage, Illinois jail.