18505 has 4 divisors (see below), whose sum is σ = 22212. Its totient is φ = 14800.

The previous prime is 18503. The next prime is 18517. The reversal of 18505 is 50581.

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 7056 + 11449 = 84^2 + 107^2 .

It is not a de Polignac number, because 18505 - 2¹ = 18503 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a nialpdrome in base 8 and base 12.

It is a zygodrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (18503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1846 + ... + 1855.

It is an arithmetic number, because the mean of its divisors is an integer number (5553).

2¹⁸⁵⁰⁵ is an apocalyptic number.

It is an amenable number.

18505 is a deficient number, since it is larger than the sum of its proper divisors (3707).

18505 is an equidigital number, since it uses as much as digits as its factorization.

18505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3706.

The product of its (nonzero) digits is 200, while the sum is 19.

The square root of 18505 is about 136.0330842112. The cubic root of 18505 is about 26.4502448391.

The spelling of 18505 in words is "eighteen thousand, five hundred five".