20650665661 has 2 divisors, whose sum is σ = 20650665662. Its totient is φ = 20650665660.

The previous prime is 20650665647. The next prime is 20650665691. The reversal of 20650665661 is 16656605602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17743838436 + 2906827225 = 133206^2 + 53915^2 .

It is a cyclic number.

It is not a de Polignac number, because 20650665661 - 2⁷ = 20650665533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20650665601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10325332830 + 10325332831.

It is an arithmetic number, because the mean of its divisors is an integer number (10325332831).

Almost surely, 2^20650665661 is an apocalyptic number.

It is an amenable number.

20650665661 is a deficient number, since it is larger than the sum of its proper divisors (1).

20650665661 is an equidigital number, since it uses as much as digits as its factorization.

20650665661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 388800, while the sum is 43.

The spelling of 20650665661 in words is "twenty billion, six hundred fifty million, six hundred sixty-five thousand, six hundred sixty-one".