Fait mathématique: 1725 is a structured deltoidal hexacontahedral number.
Culture générale: 1725 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: September 20th is the day in 1871 that Bishop John Coleridge Patteson is martyred on the island of Nukapu, a Polynesian outlier island now in the Temotu Province of the Solomon Islands.