21864638 has 4 divisors (see below), whose sum is σ = 32796960. Its totient is φ = 10932318.

The previous prime is 21864617. The next prime is 21864653. The reversal of 21864638 is 83646812.

It is a happy number.

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

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5466158 + ... + 5466161.

It is an arithmetic number, because the mean of its divisors is an integer number (8199240).

Almost surely, 2^21864638 is an apocalyptic number.

21864638 is a deficient number, since it is larger than the sum of its proper divisors (10932322).

21864638 is a wasteful number, since it uses less digits than its factorization.

21864638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10932321.

The product of its digits is 55296, while the sum is 38.

The square root of 21864638 is about 4675.9638578586. The cubic root of 21864638 is about 279.6280690989.

The spelling of 21864638 in words is "twenty-one million, eight hundred sixty-four thousand, six hundred thirty-eight".