Fatto generale: 81 is the number of squares on a shogi playing board.
Fatto matematico: 81 is the square of the sum of its digits.
Trivia: 81 is the number of squares on a shogi playing board.
Data storica: March 21st is the day in 1935 that Shah Reza Pahlavi formally asks the international community to call Persia by its native name, Iran, which means 'Land of the Aryans.