21808128 has 88 divisors (see below), whose sum is σ = 60263680. Its totient is φ = 7004160.

The previous prime is 21808123. The next prime is 21808139. The reversal of 21808128 is 82180812.

It is a junction number, because it is equal to n+sod(n) for n = 21808095 and 21808104.

It is not an unprimeable number, because it can be changed into a prime (21808121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 95118 + ... + 95346.

Almost surely, 2^21808128 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 21808128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30131840).

21808128 is an abundant number, since it is smaller than the sum of its proper divisors (38455552).

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

21808128 is a wasteful number, since it uses less digits than its factorization.

21808128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 283 (or 265 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 30.

The square root of 21808128 is about 4669.9173440223. The cubic root of 21808128 is about 279.3869580836.

The spelling of 21808128 in words is "twenty-one million, eight hundred eight thousand, one hundred twenty-eight".