21311618 has 16 divisors (see below), whose sum is σ = 32892480. Its totient is φ = 10351536.

The previous prime is 21311611. The next prime is 21311621. The reversal of 21311618 is 81611312.

It is a junction number, because it is equal to n+sod(n) for n = 21311593 and 21311602.

It is not an unprimeable number, because it can be changed into a prime (21311611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10403 + ... + 12281.

It is an arithmetic number, because the mean of its divisors is an integer number (2055780).

Almost surely, 2^21311618 is an apocalyptic number.

21311618 is a deficient number, since it is larger than the sum of its proper divisors (11580862).

21311618 is a wasteful number, since it uses less digits than its factorization.

21311618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2041.

The product of its digits is 288, while the sum is 23.

The square root of 21311618 is about 4616.4508012108. The cubic root of 21311618 is about 277.2503742227.

The spelling of 21311618 in words is "twenty-one million, three hundred eleven thousand, six hundred eighteen".