21518636 has 12 divisors (see below), whose sum is σ = 38368512. Its totient is φ = 10556208.

The previous prime is 21518611. The next prime is 21518647. The reversal of 21518636 is 63681512.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50540 + ... + 50963.

It is an arithmetic number, because the mean of its divisors is an integer number (3197376).

Almost surely, 2^21518636 is an apocalyptic number.

It is an amenable number.

21518636 is a deficient number, since it is larger than the sum of its proper divisors (16849876).

21518636 is a wasteful number, since it uses less digits than its factorization.

21518636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101560 (or 101558 counting only the distinct ones).

The product of its digits is 8640, while the sum is 32.

The square root of 21518636 is about 4638.8183840284. The cubic root of 21518636 is about 278.1452064770.

The spelling of 21518636 in words is "twenty-one million, five hundred eighteen thousand, six hundred thirty-six".