993 has 4 divisors (see below), whose sum is σ = 1328.
Its totient is φ = 660.
The previous prime is 991. The next prime is 997. The reversal of 993 is 399.
993 is nontrivially palindromic in base 13.
It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.
It is not a de Polignac number, because 993 - 21 = 991 is a prime.
It is a D-number.
It is the 32-nd Hogben number.
It is a Duffinian number.
993 is an undulating number in base 13.
It is a Curzon number.
993 is a lucky number.
It is a nialpdrome in base 6 and base 10.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 993.
It is not an unprimeable number, because it can be changed into a prime (991) by changing a digit.
It is a nontrivial repunit in base 31.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 163 + ... + 168.
It is an arithmetic number, because the mean of its divisors is an integer number (332).
It is a Proth number, since it is equal to 31 ⋅ 25 + 1 and 31 < 25.
It is an amenable number.
993 is a deficient number, since it is larger than the sum of its proper divisors (335).
993 is a wasteful number, since it uses less digits than its factorization.
993 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 334.
The product of its digits is 243, while the sum is 21.
The square root of 993 is about 31.5119025132.
The cubic root of 993 is about 9.9766120095.
The spelling of 993 in words is "nine hundred ninety-three", and thus it is an aban number and an oban number.