21163856 has 40 divisors (see below), whose sum is σ = 47121984. Its totient is φ = 9020160.

The previous prime is 21163847. The next prime is 21163859. The reversal of 21163856 is 65836112.

21163856 = 189² + 190² + ... + 412².

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21163859) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25691 + ... + 26501.

Almost surely, 2^21163856 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 21163856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23560992).

21163856 is an abundant number, since it is smaller than the sum of its proper divisors (25958128).

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

21163856 is a wasteful number, since it uses less digits than its factorization.

21163856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1059 (or 1053 counting only the distinct ones).

The product of its digits is 8640, while the sum is 32.

The square root of 21163856 is about 4600.4191113419. The cubic root of 21163856 is about 276.6081249017.

Adding to 21163856 its reverse (65836112), we get a palindrome (86999968).

The spelling of 21163856 in words is "twenty-one million, one hundred sixty-three thousand, eight hundred fifty-six".