Fatto generale: 91 is the code for international direct dial phone calls to India.
Fatto matematico: 91 is the twenty-seventh distinct semiprime and the second of the form (7.q).
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 1931 that TWA Flight 599 crashes near Bazaar, Kansas killing 8 including Knute Rockne, head football coach at the University of Notre Dame.