21648816 has 80 divisors (see below), whose sum is σ = 71027200. Its totient is φ = 6184512.

The previous prime is 21648799. The next prime is 21648821. The reversal of 21648816 is 61884612.

21648816 is a `hidden beast` number, since 2 + 1 + 648 + 8 + 1 + 6 = 666.

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

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 556 + ... + 6603.

It is an arithmetic number, because the mean of its divisors is an integer number (887840).

Almost surely, 2^21648816 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 21648816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35513600).

21648816 is an abundant number, since it is smaller than the sum of its proper divisors (49378384).

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

21648816 is a wasteful number, since it uses less digits than its factorization.

21648816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7183 (or 7171 counting only the distinct ones).

The product of its digits is 18432, while the sum is 36.

The square root of 21648816 is about 4652.8288169672. The cubic root of 21648816 is about 278.7049719810.

The spelling of 21648816 in words is "twenty-one million, six hundred forty-eight thousand, eight hundred sixteen".