21682816 has 32 divisors (see below), whose sum is σ = 43920180. Its totient is φ = 10659840.

The previous prime is 21682757. The next prime is 21682823. The reversal of 21682816 is 61828612.

It can be written as a sum of positive squares in 2 ways, for example, as 16842816 + 4840000 = 4104^2 + 2200^2 .

It is a tau number, because it is divible by the number of its divisors (32).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6420 + ... + 9196.

Almost surely, 2^21682816 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 21682816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21960090).

21682816 is an abundant number, since it is smaller than the sum of its proper divisors (22237364).

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

21682816 is an equidigital number, since it uses as much as digits as its factorization.

21682816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2852 (or 2840 counting only the distinct ones).

The product of its digits is 9216, while the sum is 34.

The square root of 21682816 is about 4656.4810748032. The cubic root of 21682816 is about 278.8508000119.

The spelling of 21682816 in words is "twenty-one million, six hundred eighty-two thousand, eight hundred sixteen".