21008806 has 32 divisors (see below), whose sum is σ = 39251520. Its totient is φ = 8211456.

The previous prime is 21008797. The next prime is 21008833. The reversal of 21008806 is 60880012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15550 + ... + 16846.

It is an arithmetic number, because the mean of its divisors is an integer number (1226610).

Almost surely, 2^21008806 is an apocalyptic number.

21008806 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21008806 is a deficient number, since it is larger than the sum of its proper divisors (18242714).

21008806 is a wasteful number, since it uses less digits than its factorization.

21008806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1408.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 21008806 is about 4583.5364076224. The cubic root of 21008806 is about 275.9309758781.

Adding to 21008806 its reverse (60880012), we get a palindrome (81888818).

The spelling of 21008806 in words is "twenty-one million, eight thousand, eight hundred six".