Fatto generale: 345 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 345 is half again as large as the sum of its proper divisors.
Trivia: 345 is a boring number.
Data storica: 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.