21159856 has 40 divisors (see below), whose sum is σ = 43501184. Its totient is φ = 9953280.

The previous prime is 21159811. The next prime is 21159857. The reversal of 21159856 is 65895112.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is not an unprimeable number, because it can be changed into a prime (21159857) 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 7 ways as a sum of consecutive naturals, for example, 17776 + ... + 18928.

Almost surely, 2^21159856 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 21159856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21750592).

21159856 is an abundant number, since it is smaller than the sum of its proper divisors (22341328).

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

21159856 is a wasteful number, since it uses less digits than its factorization.

21159856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1229 (or 1223 counting only the distinct ones).

The product of its digits is 21600, while the sum is 37.

The square root of 21159856 is about 4599.9843477995. The cubic root of 21159856 is about 276.5906973559.

The spelling of 21159856 in words is "twenty-one million, one hundred fifty-nine thousand, eight hundred fifty-six".