21635856 has 160 divisors (see below), whose sum is σ = 70531200. Its totient is φ = 6289920.

The previous prime is 21635833. The next prime is 21635857. The reversal of 21635856 is 65853612.

It is a super-2 number, since 2×21635856² = 936220529705472, which contains 22 as substring.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21635856.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21635857) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 137730 + ... + 137886.

It is an arithmetic number, because the mean of its divisors is an integer number (440820).

Almost surely, 2^21635856 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 21635856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35265600).

21635856 is an abundant number, since it is smaller than the sum of its proper divisors (48895344).

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

21635856 is a wasteful number, since it uses less digits than its factorization.

21635856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214 (or 202 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 21635856 is about 4651.4359073301. The cubic root of 21635856 is about 278.6493455755.

The spelling of 21635856 in words is "twenty-one million, six hundred thirty-five thousand, eight hundred fifty-six".