Fait mathématique: 1666 is the sum of the Roman numerals.
Culture générale: 1666 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: July 23rd is the day in 1983 that the Sri Lankan Civil War begins with the killing of 13 Sri Lanka Army soldiers by the Liberation Tigers of Tamil Eelam Terrorist group.