Hecho general: 61561 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 61561 is an unremarkable number.
Trivia: 61561 is a boring number.
Fecha histórica: July 18th is the day in 1914 that the U.S. Congress forms the Aviation Section, U.S. Signal Corps, giving definite status to aircraft within the U.S. Army for the first time.