21968208 has 60 divisors (see below), whose sum is σ = 61796020. Its totient is φ = 7285248.

The previous prime is 21968203. The next prime is 21968209. The reversal of 21968208 is 80286912.

It can be written as a sum of positive squares in 2 ways, for example, as 16548624 + 5419584 = 4068^2 + 2328^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21968203) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 53508 + ... + 53916.

Almost surely, 2^21968208 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21968208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30898010).

21968208 is an abundant number, since it is smaller than the sum of its proper divisors (39827812).

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

21968208 is a wasteful number, since it uses less digits than its factorization.

21968208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 796 (or 787 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 36.

The square root of 21968208 is about 4687.0254959836. The cubic root of 21968208 is about 280.0688946116.

It can be divided in two parts, 2196 and 8208, that added together give a square (10404 = 102²).

The spelling of 21968208 in words is "twenty-one million, nine hundred sixty-eight thousand, two hundred eight".