21804638 has 8 divisors (see below), whose sum is σ = 32729832. Its totient is φ = 10894696.

The previous prime is 21804637. The next prime is 21804641. The reversal of 21804638 is 83640812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21804638² = 950884476622088, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21804637) 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, 956 + ... + 6672.

It is an arithmetic number, because the mean of its divisors is an integer number (4091229).

Almost surely, 2^21804638 is an apocalyptic number.

21804638 is a deficient number, since it is larger than the sum of its proper divisors (10925194).

21804638 is a wasteful number, since it uses less digits than its factorization.

21804638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7626.

The product of its (nonzero) digits is 9216, while the sum is 32.

The square root of 21804638 is about 4669.5436607874. The cubic root of 21804638 is about 279.3720536635.

The spelling of 21804638 in words is "twenty-one million, eight hundred four thousand, six hundred thirty-eight".