21118636 has 24 divisors (see below), whose sum is σ = 46077696. Its totient is φ = 8227920.

The previous prime is 21118619. The next prime is 21118661. The reversal of 21118636 is 63681112.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33976 + ... + 34591.

It is an arithmetic number, because the mean of its divisors is an integer number (1919904).

Almost surely, 2^21118636 is an apocalyptic number.

It is an amenable number.

21118636 is an abundant number, since it is smaller than the sum of its proper divisors (24959060).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21118636 is a wasteful number, since it uses less digits than its factorization.

21118636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68589 (or 68587 counting only the distinct ones).

The product of its digits is 1728, while the sum is 28.

The square root of 21118636 is about 4595.5017136326. The cubic root of 21118636 is about 276.4109784301.

Adding to 21118636 its reverse (63681112), we get a palindrome (84799748).

The spelling of 21118636 in words is "twenty-one million, one hundred eighteen thousand, six hundred thirty-six".