20656439661 has 64 divisors (see below), whose sum is σ = 33633976320. Its totient is φ = 11107549440.

The previous prime is 20656439651. The next prime is 20656439669. The reversal of 20656439661 is 16693465602.

It is a happy number.

It is not a de Polignac number, because 20656439661 - 2²⁵ = 20622885229 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20656439661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20656439669) 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 63 ways as a sum of consecutive naturals, for example, 1309620 + ... + 1325298.

It is an arithmetic number, because the mean of its divisors is an integer number (525530880).

Almost surely, 2^20656439661 is an apocalyptic number.

It is an amenable number.

20656439661 is a deficient number, since it is larger than the sum of its proper divisors (12977536659).

20656439661 is a wasteful number, since it uses less digits than its factorization.

20656439661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15826.

The product of its (nonzero) digits is 1399680, while the sum is 48.

The spelling of 20656439661 in words is "twenty billion, six hundred fifty-six million, four hundred thirty-nine thousand, six hundred sixty-one".