21679856 has 40 divisors (see below), whose sum is σ = 46128000. Its totient is φ = 9789120.

The previous prime is 21679843. The next prime is 21679871. The reversal of 21679856 is 65897612.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 34715 + ... + 35333.

It is an arithmetic number, because the mean of its divisors is an integer number (1153200).

Almost surely, 2^21679856 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 21679856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23064000).

21679856 is an abundant number, since it is smaller than the sum of its proper divisors (24448144).

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

21679856 is a wasteful number, since it uses less digits than its factorization.

21679856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 837 (or 831 counting only the distinct ones).

The product of its digits is 181440, while the sum is 44.

The square root of 21679856 is about 4656.1632273794. The cubic root of 21679856 is about 278.8381104558.

The spelling of 21679856 in words is "twenty-one million, six hundred seventy-nine thousand, eight hundred fifty-six".