21943656 has 128 divisors (see below), whose sum is σ = 72806400. Its totient is φ = 5987520.

The previous prime is 21943637. The next prime is 21943673. The reversal of 21943656 is 65634912.

It is a happy number.

21943656 is a `hidden beast` number, since 219 + 436 + 5 + 6 = 666.

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 21943656.

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 31 ways as a sum of consecutive naturals, for example, 34461 + ... + 35091.

It is an arithmetic number, because the mean of its divisors is an integer number (568800).

Almost surely, 2^21943656 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 21943656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36403200).

21943656 is an abundant number, since it is smaller than the sum of its proper divisors (50862744).

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

21943656 is a wasteful number, since it uses less digits than its factorization.

21943656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 676 (or 666 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 21943656 is about 4684.4056186458. The cubic root of 21943656 is about 279.9645193137.

The spelling of 21943656 in words is "twenty-one million, nine hundred forty-three thousand, six hundred fifty-six".