21243600656 has 20 divisors (see below), whose sum is σ = 43580622492. Its totient is φ = 9996988416.

The previous prime is 21243600619. The next prime is 21243600667. The reversal of 21243600656 is 65600634212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 7899654400 + 13343946256 = 88880^2 + 115516^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39050465 + ... + 39051008.

Almost surely, 2^21243600656 is an apocalyptic number.

It is an amenable number.

21243600656 is an abundant number, since it is smaller than the sum of its proper divisors (22337021836).

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

21243600656 is a wasteful number, since it uses less digits than its factorization.

21243600656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78101498 (or 78101492 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 35.

The spelling of 21243600656 in words is "twenty-one billion, two hundred forty-three million, six hundred thousand, six hundred fifty-six".