21918618 has 24 divisors (see below), whose sum is σ = 48297600. Its totient is φ = 7182024.

The previous prime is 21918607. The next prime is 21918649. The reversal of 21918618 is 81681912.

21918618 is a `hidden beast` number, since 21 + 9 + 18 + 618 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9258 + ... + 11381.

It is an arithmetic number, because the mean of its divisors is an integer number (2012400).

Almost surely, 2^21918618 is an apocalyptic number.

21918618 is an abundant number, since it is smaller than the sum of its proper divisors (26378982).

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

21918618 is a wasteful number, since it uses less digits than its factorization.

21918618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20706 (or 20703 counting only the distinct ones).

The product of its digits is 6912, while the sum is 36.

The square root of 21918618 is about 4681.7323716761. The cubic root of 21918618 is about 279.8579977235.

The spelling of 21918618 in words is "twenty-one million, nine hundred eighteen thousand, six hundred eighteen".