Fait mathématique: 2780 is 1^{8} + 2^{7} + 3^{6} + 4^{5} + 5^{4} + 6^{3} + 7^{2} + 8^{1}.
Culture générale: 2780 is an uninteresting number.
Date historique: August 11th is the day in 1920 that the Latvian–Soviet Peace Treaty, which relinquished Russia's authority and pretenses to Latvia, is signed, ending the Latvian War of Independence.