Fatto matematico: 806 is not the sum of a square, a cube, a 4^{th} power, and a 5^{th} power.
Trivia: 806 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 455 that Emperor Valentinian III is assassinated by two Hunnic retainers while training with the bow on the Campus Martius (Rome).