Hecho matemático: 515 is the number of graphs on 6 vertices with no isolated vertices.
Trivia: 515 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fecha histórica: May 29th is the day in 1167 that Battle of Monte Porzio – A Roman army supporting Pope Alexander III is defeated by Christian of Buch and Rainald of Dassel.