Fatto matematico: 2811 is the number of inequivalent Ferrers graphs with 30 points.
Trivia: 2811 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: September 11th is the day in 1708 that Charles XII of Sweden stops his march to conquer Moscow outside Smolensk, marking the turning point in the Great Northern War.