21638013 has 8 divisors (see below), whose sum is σ = 28876800. Its totient is φ = 14412288.

The previous prime is 21637997. The next prime is 21638033. The reversal of 21638013 is 31083612.

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

It is not a de Polignac number, because 21638013 - 2⁴ = 21637997 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21638033) 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, 1668 + ... + 6786.

It is an arithmetic number, because the mean of its divisors is an integer number (3609600).

Almost surely, 2^21638013 is an apocalyptic number.

It is an amenable number.

21638013 is a deficient number, since it is larger than the sum of its proper divisors (7238787).

21638013 is a wasteful number, since it uses less digits than its factorization.

21638013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6531.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21638013 is about 4651.6677654364. The cubic root of 21638013 is about 278.6586053072.

The spelling of 21638013 in words is "twenty-one million, six hundred thirty-eight thousand, thirteen".