21010808 has 128 divisors (see below), whose sum is σ = 53760000. Its totient is φ = 7620480.

The previous prime is 21010763. The next prime is 21010811. The reversal of 21010808 is 80801012.

It is a self number, because there is not a number n which added to its sum of digits gives 21010808.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 677753 + ... + 677783.

It is an arithmetic number, because the mean of its divisors is an integer number (420000).

Almost surely, 2^21010808 is an apocalyptic number.

21010808 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21010808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26880000).

21010808 is an abundant number, since it is smaller than the sum of its proper divisors (32749192).

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

21010808 is a wasteful number, since it uses less digits than its factorization.

21010808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90 (or 72 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 20.

The square root of 21010808 is about 4583.7547927436. The cubic root of 21010808 is about 275.9397403975.

The spelling of 21010808 in words is "twenty-one million, ten thousand, eight hundred eight".