Hecho matemático: 821 is a number n for which n, n+2, n+6, and n+8 are all prime.
Trivia: 821 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fecha histórica: March 31st is the day in 1992 that the USS Missouri, the last active United States Navy battleship, is decommissioned in Long Beach, California.