Fatto generale: 61616 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 61616 is a boring number.
Trivia: 61616 is an unremarkable number.
Data storica: September 11th is the day in 1932 that Franciszek Żwirko and Stanisław Wigura, Polish Challenge 1932 winners, are killed when their RWD 6 airplane crashes during a storm.