General fact: 81 is the number of squares on a shogi playing board.
Mathematical fact: 81 is the square of the sum of its digits.
Trivia: 81 is the number of stanzas or chapters in the Tao te Ching (in the most common arrangements).
Historical date: March 21st is the day in 1925 that Syngman Rhee is removed from office after being impeached as the President of the Provisional Government of the Republic of Korea.