• Hexadecimal: 59
• Binary: 01011001
• Factors: 1, 89.
• the 24th prime number, following eighty-three and preceeding ninety-seven, a Sophie Germain prime, a Fibonacci number
• Ordinal number: eighty-ninth

89 is also:

• the atomic number of actinium (Ac)
• the model number of CBU-89 Gator, TI-89
• part of the name of the baseball team Oklahoma City 89ers (1962-1997)
• the number of the French department Yonne
• the designation of Interstate 89, a freeway that runs from New Hampshire to Vermont
• the year AD 89, 1889, or 1989.