Fatto matematico: 7746 is the number permutations of {1,2,3,...,21} where adjacent numbers differ by no more than 2.
Trivia: 7746 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: March 16th is the day in 1995 that Mississippi formally ratified the Thirteenth Amendment, becoming the last state to approve the abolition of slavery.