Mathematical fact: 2176 is the number of prime knots with 12 crossings.
Trivia: 2176 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Historical date: December 15th is the day in 1997 that a chartered Tupolev TU-154 from Tajikistan crashes in the desert near Sharja, United Arab Emirates airport killing 85.