20643500656 has 160 divisors (see below), whose sum is σ = 45153110016. Its totient is φ = 9096192000.

The previous prime is 20643500653. The next prime is 20643500659. The reversal of 20643500656 is 65600534602.

It is an interprime number because it is at equal distance from previous prime (20643500653) and next prime (20643500659).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20643500653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 72945091 + ... + 72945373.

Almost surely, 2^20643500656 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 20643500656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22576555008).

20643500656 is an abundant number, since it is smaller than the sum of its proper divisors (24509609360).

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

20643500656 is a wasteful number, since it uses less digits than its factorization.

20643500656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 591 (or 585 counting only the distinct ones).

The product of its (nonzero) digits is 129600, while the sum is 37.

The spelling of 20643500656 in words is "twenty billion, six hundred forty-three million, five hundred thousand, six hundred fifty-six".