21072808 has 24 divisors (see below), whose sum is σ = 40842090. Its totient is φ = 10192800.

The previous prime is 21072769. The next prime is 21072823. The reversal of 21072808 is 80827012.

It can be written as a sum of positive squares in only one way, i.e., 19377604 + 1695204 = 4402^2 + 1302^2 .

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

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, 6318 + ... + 9058.

Almost surely, 2^21072808 is an apocalyptic number.

It is an amenable number.

21072808 is a deficient number, since it is larger than the sum of its proper divisors (19769282).

21072808 is a wasteful number, since it uses less digits than its factorization.

21072808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2809 (or 2774 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 28.

The square root of 21072808 is about 4590.5128253824. The cubic root of 21072808 is about 276.2108939136.

The spelling of 21072808 in words is "twenty-one million, seventy-two thousand, eight hundred eight".