21008856 has 32 divisors (see below), whose sum is σ = 57297600. Its totient is φ = 6366240.

The previous prime is 21008849. The next prime is 21008857. The reversal of 21008856 is 65880012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21008857) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39526 + ... + 40053.

It is an arithmetic number, because the mean of its divisors is an integer number (1790550).

Almost surely, 2^21008856 is an apocalyptic number.

It is an amenable number.

21008856 is an abundant number, since it is smaller than the sum of its proper divisors (36288744).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21008856 is a wasteful number, since it uses less digits than its factorization.

21008856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79599 (or 79595 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 30.

The square root of 21008856 is about 4583.5418619229. The cubic root of 21008856 is about 275.9311947789.

Adding to 21008856 its reverse (65880012), we get a palindrome (86888868).

The spelling of 21008856 in words is "twenty-one million, eight thousand, eight hundred fifty-six".