Fatto generale: 91 is the amount of money one has if one has one coin of each U.S. denomination less than a dollar (penny, nickel, dime, quarter, half dollar) in cents.
Fatto matematico: 91 is the smallest pseudoprime in base 3.
Trivia: 91 is the amount of money one has if one has one coin of each U.S. denomination less than a dollar (penny, nickel, dime, quarter, half dollar) in cents.
Data storica: March 31st is the day in 1877 that the family with samurai antecedents that responded to the Saigō army in Ōita Nakatsu, rebels.