21918208 has 80 divisors (see below), whose sum is σ = 48981240. Its totient is φ = 9732096.

The previous prime is 21918187. The next prime is 21918233. The reversal of 21918208 is 80281912.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 16386304 + 5531904 = 4048^2 + 2352^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21918208.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 246228 + ... + 246316.

Almost surely, 2^21918208 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 21918208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24490620).

21918208 is an abundant number, since it is smaller than the sum of its proper divisors (27063032).

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

21918208 is an equidigital number, since it uses as much as digits as its factorization.

21918208 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157 (or 141 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 21918208 is about 4681.6885842610. The cubic root of 21918208 is about 279.8562527458.

The spelling of 21918208 in words is "twenty-one million, nine hundred eighteen thousand, two hundred eight".