18981918 has 16 divisors (see below), whose sum is σ = 42182160. Its totient is φ = 6327288.

The previous prime is 18981901. The next prime is 18981929. The reversal of 18981918 is 81918981.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175705 + ... + 175812.

It is an arithmetic number, because the mean of its divisors is an integer number (2636385).

Almost surely, 2^18981918 is an apocalyptic number.

18981918 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

18981918 is an abundant number, since it is smaller than the sum of its proper divisors (23200242).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18981918 is a wasteful number, since it uses less digits than its factorization.

18981918 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 351528 (or 351522 counting only the distinct ones).

The product of its digits is 41472, while the sum is 45.

The square root of 18981918 is about 4356.8243021724. The cubic root of 18981918 is about 266.7554888143.

The spelling of 18981918 in words is "eighteen million, nine hundred eighty-one thousand, nine hundred eighteen".