Fait général: 2751 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 2751 is the number of ordered partitions of 21 into distinct parts.
Culture générale: 2751 is an uninteresting number.
Date historique: July 13th is the day in 1985 that the Live Aid benefit concert takes place in London and Philadelphia, as well as other venues such as Sydney and Moscow.