21638636 has 24 divisors (see below), whose sum is σ = 39102000. Its totient is φ = 10469952.

The previous prime is 21638633. The next prime is 21638647. The reversal of 21638636 is 63683612.

It is a junction number, because it is equal to n+sod(n) for n = 21638596 and 21638605.

It is not an unprimeable number, because it can be changed into a prime (21638633) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 43115 + ... + 43613.

It is an arithmetic number, because the mean of its divisors is an integer number (1629250).

Almost surely, 2^21638636 is an apocalyptic number.

It is an amenable number.

21638636 is a deficient number, since it is larger than the sum of its proper divisors (17463364).

21638636 is a wasteful number, since it uses less digits than its factorization.

21638636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 833 (or 831 counting only the distinct ones).

The product of its digits is 31104, while the sum is 35.

The square root of 21638636 is about 4651.7347301840. The cubic root of 21638636 is about 278.6612796539.

The spelling of 21638636 in words is "twenty-one million, six hundred thirty-eight thousand, six hundred thirty-six".