Fatto generale: 841 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 841 is a square that is also the sum of 2 consecutive squares.
Trivia: 841 is a boring number.
Data storica: April 20th is the day in 1984 that the Good Friday Massacre, an extremely violent ice hockey playoff game, is played in Montreal, Canada.