Hecho general: 6650 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 6650 is a boring number.
Trivia: 6650 is an uninteresting number.
Fecha histórica: March 16th is the day in 1916 that the 7th and 10th US cavalry regiments under John J. Pershing crossed the US-Mexico border to join the hunt for Pancho Villa.