20656656617 has 4 divisors (see below), whose sum is σ = 20657075796. Its totient is φ = 20656237440.

The previous prime is 20656656593. The next prime is 20656656619. The reversal of 20656656617 is 71665665602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 71665665602 = 2 ⋅35832832801.

It can be written as a sum of positive squares in 2 ways, for example, as 11540990041 + 9115666576 = 107429^2 + 95476^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20656656617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20656656619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 124028 + ... + 238109.

It is an arithmetic number, because the mean of its divisors is an integer number (5164268949).

Almost surely, 2^20656656617 is an apocalyptic number.

It is an amenable number.

20656656617 is a deficient number, since it is larger than the sum of its proper divisors (419179).

20656656617 is an equidigital number, since it uses as much as digits as its factorization.

20656656617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 419178.

The product of its (nonzero) digits is 2721600, while the sum is 50.

The spelling of 20656656617 in words is "twenty billion, six hundred fifty-six million, six hundred fifty-six thousand, six hundred seventeen".