Fatto generale: 6837 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 6837 is the number of 8-digit squares.
Trivia: 6837 is an unremarkable number.
Data storica: September 19th is the day in 1940 that Witold Pilecki is voluntarily captured and sent to Auschwitz in order to smuggle out information and start a resistance.