Hecho general: 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.
Hecho matemático: 91 is the twenty-seventh distinct semiprime and the second of the form (7.q).
Trivia: 91 is the code for international direct dial phone calls to India.
Fecha histórica: March 31st is the day in 1717 that a sermon on "The Nature of the Kingdom of Christ" by Benjamin Hoadly, the Bishop of Bangor, provokes the Bangorian Controversy.