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 an uninteresting number.
Data storica: April 20th is the day in 2010 that the Deepwater Horizon oil well explodes in the Gulf of Mexico, killing twelve workers and beginning an oil spill that would last six months.