18331 has 4 divisors (see below), whose sum is σ = 19152. Its totient is φ = 17512.

The previous prime is 18329. The next prime is 18341. The reversal of 18331 is 13381.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 18331 - 2¹ = 18329 is a prime.

It is a super-2 number, since 2×18331² = 672051122, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (18301) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 376 + ... + 421.

It is an arithmetic number, because the mean of its divisors is an integer number (4788).

2¹⁸³³¹ is an apocalyptic number.

18331 is a deficient number, since it is larger than the sum of its proper divisors (821).

18331 is an equidigital number, since it uses as much as digits as its factorization.

18331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 820.

The product of its digits is 72, while the sum is 16.

The square root of 18331 is about 135.3920233987. The cubic root of 18331 is about 26.3670809465.

Subtracting from 18331 its reverse (13381), we obtain a triangular number (4950 = T₉₉).

The spelling of 18331 in words is "eighteen thousand, three hundred thirty-one".