Fatto matematico: 615 is the trinomial coefficient T(10,6).
Trivia: 615 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: September 6th is the day in 1901 that Anarchist Leon Czolgosz shoots and fatally wounds US President William McKinley at the Pan-American Exposition in Buffalo, New York.