21008864 has 12 divisors (see below), whose sum is σ = 41361264. Its totient is φ = 10504416.

The previous prime is 21008857. The next prime is 21008879. The reversal of 21008864 is 46880012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 328232 + ... + 328295.

It is an arithmetic number, because the mean of its divisors is an integer number (3446772).

Almost surely, 2^21008864 is an apocalyptic number.

It is an amenable number.

21008864 is a deficient number, since it is larger than the sum of its proper divisors (20352400).

21008864 is an equidigital number, since it uses as much as digits as its factorization.

21008864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 656537 (or 656529 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 21008864 is about 4583.5427346104. The cubic root of 21008864 is about 275.9312298031.

Adding to 21008864 its reverse (46880012), we get a palindrome (67888876).

The spelling of 21008864 in words is "twenty-one million, eight thousand, eight hundred sixty-four".