18008981 has 4 divisors (see below), whose sum is σ = 18150912. Its totient is φ = 17867052.

The previous prime is 18008917. The next prime is 18008989. The reversal of 18008981 is 18980081.

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: 18980081 = 1327 ⋅14303.

It is a cyclic number.

It is not a de Polignac number, because 18008981 - 2⁶ = 18008917 is a prime.

It is a super-2 number, since 2×18008981² = 648646793316722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18008989) 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, 70775 + ... + 71028.

It is an arithmetic number, because the mean of its divisors is an integer number (4537728).

Almost surely, 2^18008981 is an apocalyptic number.

It is an amenable number.

18008981 is a deficient number, since it is larger than the sum of its proper divisors (141931).

18008981 is a wasteful number, since it uses less digits than its factorization.

18008981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141930.

The product of its (nonzero) digits is 4608, while the sum is 35.

The square root of 18008981 is about 4243.6989761292. The cubic root of 18008981 is about 262.1177189857.

The spelling of 18008981 in words is "eighteen million, eight thousand, nine hundred eighty-one".