21028808 has 24 divisors (see below), whose sum is σ = 41226150. Its totient is φ = 10055232.

The previous prime is 21028771. The next prime is 21028823. The reversal of 21028808 is 80882012.

It can be written as a sum of positive squares in only one way, i.e., 19909444 + 1119364 = 4462^2 + 1058^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1748 + ... + 6716.

Almost surely, 2^21028808 is an apocalyptic number.

It is an amenable number.

21028808 is a deficient number, since it is larger than the sum of its proper divisors (20197342).

21028808 is a wasteful number, since it uses less digits than its factorization.

21028808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5021 (or 4994 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 29.

The square root of 21028808 is about 4585.7178282140. The cubic root of 21028808 is about 276.0185172761.

The spelling of 21028808 in words is "twenty-one million, twenty-eight thousand, eight hundred eight".