18665 has 4 divisors (see below), whose sum is σ = 22404. Its totient is φ = 14928.

The previous prime is 18661. The next prime is 18671. The reversal of 18665 is 56681.

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

It can be written as a sum of positive squares in 2 ways, for example, as 8464 + 10201 = 92^2 + 101^2 .

It is a cyclic number.

It is not a de Polignac number, because 18665 - 2² = 18661 is a prime.

It is a Duffinian number.

It is a plaindrome in base 6.

It is a nialpdrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (18661) 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, 1862 + ... + 1871.

It is an arithmetic number, because the mean of its divisors is an integer number (5601).

2¹⁸⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

18665 is a deficient number, since it is larger than the sum of its proper divisors (3739).

18665 is an equidigital number, since it uses as much as digits as its factorization.

18665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3738.

The product of its digits is 1440, while the sum is 26.

The square root of 18665 is about 136.6199107012. The cubic root of 18665 is about 26.5262585337.

It can be divided in two parts, 186 and 65, that multiplied together give a triangular number (12090 = T₁₅₅).

The spelling of 18665 in words is "eighteen thousand, six hundred sixty-five".