21806928 has 160 divisors (see below), whose sum is σ = 73745280. Its totient is φ = 6082560.

The previous prime is 21806909. The next prime is 21806929. The reversal of 21806928 is 82960812.

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

It is a junction number, because it is equal to n+sod(n) for n = 21806892 and 21806901.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21806929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 61600 + ... + 61952.

It is an arithmetic number, because the mean of its divisors is an integer number (460908).

Almost surely, 2^21806928 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 21806928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36872640).

21806928 is an abundant number, since it is smaller than the sum of its proper divisors (51938352).

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

21806928 is a wasteful number, since it uses less digits than its factorization.

21806928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 394 (or 382 counting only the distinct ones).

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

The square root of 21806928 is about 4669.7888603233. The cubic root of 21806928 is about 279.3818335340.

The spelling of 21806928 in words is "twenty-one million, eight hundred six thousand, nine hundred twenty-eight".