53 (fifty-three) is the natural number following 52 and preceding 54. It is the 16th prime number.
53 is a prime number, a balanced prime, and an isolated prime.
53 is a sexy prime with 47 and 59. It is the eighth Sophie Germain prime, and the ninth Eisenstein prime.
53 is the smallest prime number that does not divide the order of any sporadic group, inclusive of the six pariahs; it is also the first prime number that is not a member of Bhargava's prime-universality criterion theorem (followed by the next prime number 59), an integer-matrix quadratic form that represents all prime numbers when it represents the sequence of seventeen integers {2, ..., 47, 67, 73}.