18631 has 4 divisors (see below), whose sum is σ = 19264. Its totient is φ = 18000.

The previous prime is 18617. The next prime is 18637. The reversal of 18631 is 13681.

18631 = T₁₈ + T₁₉ + ... + T₄₈.

18631 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

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

It is a 4-Lehmer number, since φ(18631) divides (18631-1)⁴.

It is a cyclic number.

It is not a de Polignac number, because 18631 - 2⁷ = 18503 is a prime.

It is a super-2 number, since 2×18631² = 694228322, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 18599 and 18608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18637) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 270 + ... + 331.

It is an arithmetic number, because the mean of its divisors is an integer number (4816).

2¹⁸⁶³¹ is an apocalyptic number.

18631 is a deficient number, since it is larger than the sum of its proper divisors (633).

18631 is an equidigital number, since it uses as much as digits as its factorization.

18631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 632.

The product of its digits is 144, while the sum is 19.

The square root of 18631 is about 136.4954211686. The cubic root of 18631 is about 26.5101420773.

Subtracting from 18631 its reverse (13681), we obtain a triangular number (4950 = T₉₉).

The spelling of 18631 in words is "eighteen thousand, six hundred thirty-one".