18159881 has 4 divisors (see below), whose sum is σ = 18430992. Its totient is φ = 17888772.

The previous prime is 18159863. The next prime is 18159917. The reversal of 18159881 is 18895181.

It is a happy number.

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: 18895181 = 101 ⋅187081.

It is a cyclic number.

It is not a de Polignac number, because 18159881 - 2¹⁴ = 18143497 is a prime.

It is a super-2 number, since 2×18159881² = 659562555868322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18159851) 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, 135455 + ... + 135588.

It is an arithmetic number, because the mean of its divisors is an integer number (4607748).

Almost surely, 2^18159881 is an apocalyptic number.

It is an amenable number.

18159881 is a deficient number, since it is larger than the sum of its proper divisors (271111).

18159881 is an equidigital number, since it uses as much as digits as its factorization.

18159881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 271110.

The product of its digits is 23040, while the sum is 41.

The square root of 18159881 is about 4261.4411881428. The cubic root of 18159881 is about 262.8477917588.

The spelling of 18159881 in words is "eighteen million, one hundred fifty-nine thousand, eight hundred eighty-one".