21115564 has 36 divisors (see below), whose sum is σ = 40970664. Its totient is φ = 9488512.

The previous prime is 21115559. The next prime is 21115573. The reversal of 21115564 is 46551112.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 35679 + ... + 36265.

It is an arithmetic number, because the mean of its divisors is an integer number (1138074).

Almost surely, 2^21115564 is an apocalyptic number.

It is an amenable number.

21115564 is a deficient number, since it is larger than the sum of its proper divisors (19855100).

21115564 is a wasteful number, since it uses less digits than its factorization.

21115564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 654 (or 629 counting only the distinct ones).

The product of its digits is 1200, while the sum is 25.

The square root of 21115564 is about 4595.1674615840. The cubic root of 21115564 is about 276.3975751702.

Adding to 21115564 its reverse (46551112), we get a palindrome (67666676).

The spelling of 21115564 in words is "twenty-one million, one hundred fifteen thousand, five hundred sixty-four".