21904618 has 4 divisors (see below), whose sum is σ = 32856930. Its totient is φ = 10952308.

The previous prime is 21904609. The next prime is 21904643. The reversal of 21904618 is 81640912.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 13935289 + 7969329 = 3733^2 + 2823^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21904618.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5476153 + ... + 5476156.

Almost surely, 2^21904618 is an apocalyptic number.

21904618 is a deficient number, since it is larger than the sum of its proper divisors (10952312).

21904618 is a wasteful number, since it uses less digits than its factorization.

21904618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10952311.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 21904618 is about 4680.2369598130. The cubic root of 21904618 is about 279.7984008024.

It can be divided in two parts, 21904 and 618, that added together give a palindrome (22522).

The spelling of 21904618 in words is "twenty-one million, nine hundred four thousand, six hundred eighteen".