18158561 has 4 divisors (see below), whose sum is σ = 18253824. Its totient is φ = 18063300.

The previous prime is 18158549. The next prime is 18158563. The reversal of 18158561 is 16585181.

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, and also an emirpimes, since its reverse is a distinct semiprime: 16585181 = 79 ⋅209939.

It is a cyclic number.

It is not a de Polignac number, because 18158561 - 2¹⁴ = 18142177 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18158563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 47345 + ... + 47726.

It is an arithmetic number, because the mean of its divisors is an integer number (4563456).

Almost surely, 2^18158561 is an apocalyptic number.

It is an amenable number.

18158561 is a deficient number, since it is larger than the sum of its proper divisors (95263).

18158561 is an equidigital number, since it uses as much as digits as its factorization.

18158561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95262.

The product of its digits is 9600, while the sum is 35.

The square root of 18158561 is about 4261.2863081469. The cubic root of 18158561 is about 262.8414230039.

The spelling of 18158561 in words is "eighteen million, one hundred fifty-eight thousand, five hundred sixty-one".