18985881 has 4 divisors (see below), whose sum is σ = 25314512. Its totient is φ = 12657252.

The previous prime is 18985877. The next prime is 18985909. The reversal of 18985881 is 18858981.

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: 18858981 = 3 ⋅6286327.

It is not a de Polignac number, because 18985881 - 2² = 18985877 is a prime.

It is a super-2 number, since 2×18985881² = 720927354692322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18985881.

It is not an unprimeable number, because it can be changed into a prime (18985831) 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, 3164311 + ... + 3164316.

It is an arithmetic number, because the mean of its divisors is an integer number (6328628).

Almost surely, 2^18985881 is an apocalyptic number.

It is an amenable number.

18985881 is a deficient number, since it is larger than the sum of its proper divisors (6328631).

18985881 is an equidigital number, since it uses as much as digits as its factorization.

18985881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6328630.

The product of its digits is 184320, while the sum is 48.

The square root of 18985881 is about 4357.2790821796. The cubic root of 18985881 is about 266.7740517162.

The spelling of 18985881 in words is "eighteen million, nine hundred eighty-five thousand, eight hundred eighty-one".