Fatto matematico: 21015 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 21015 is an uninteresting number.
Data storica: July 14th is the day in 1916 that Start of the Battle of Delville Wood as an action within the Battle of the Somme, which was to last until 3 September 1916.