93 (ninety-three) is the natural number following 92 and preceding 94.

In mathematics

93 is:

• the 28th distinct semiprime^[1] and the 9th of the form (3.q) where q is a higher prime.^[2]
• the first number in the 3rd triplet of consecutive semiprimes, 93, 94, 95.^[3]
• with an aliquot sum of 35; itself a semiprime, within an aliquot sequence (93,35,13,1,0) of three numbers to the Prime 13 in the 13-Aliquot tree.
• a Blum integer, since its two prime factors, 3 and 31 are both Gaussian primes.^[4]
• a repdigit in base 5 (333₅),^[5] and 30 (33₃₀).
• palindromic in bases 2, 5, and 30.
• a lucky number.^[6]
• a cake number.^[7]
• an idoneal number.^[8]

There are 93 different cyclic Gilbreath permutations on 11 elements,^[9] and therefore there are 93 different real periodic points of order 11 on the Mandelbrot set.^[10]

In other fields

Ninety-three is:

• The atomic number of neptunium, an actinide.
• The code for international direct dial phone calls to Afghanistan.
• One of two ISBN Group Identifiers for books published in India.
• The number of the French department Seine-Saint-Denis, a Paris suburb with high proportions of immigrants and low-income people, and as such used by many French rappers and those emulating their speech.^[11][12]

In classical Persian finger counting, the number 93 is represented by a closed fist. Because of this, classical Arab and Persian poets around 1 CE referred to someone's lack of generosity by saying that the person's hand made "ninety-three".^[13]