Mathematical fact: 669 is the number of unsymmetrical ways to dissect a regular 12-gon into 10 triangles.
Trivia: 669 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Historical date: October 30th is the day in 1938 that Orson Welles broadcasts his radio play of H. G. Wells's The War of the Worlds, causing anxiety in some of the audience in the United States.