Hecho matemático: 345 is half again as large as the sum of its proper divisors.
Trivia: 345 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fecha histórica: December 10th is the day in 1989 that Tsakhiagiin Elbegdorj announces the establishment of Mongolia's democratic movement that changes the second oldest communist country into a democracy.