20656666517 has 2 divisors, whose sum is σ = 20656666518. Its totient is φ = 20656666516.

The previous prime is 20656666501. The next prime is 20656666529. The reversal of 20656666517 is 71566665602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13240184356 + 7416482161 = 115066^2 + 86119^2 .

It is a cyclic number.

It is not a de Polignac number, because 20656666517 - 2⁴ = 20656666501 is a prime.

It is a super-2 number, since 2×20656666517² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20656696517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10328333258 + 10328333259.

It is an arithmetic number, because the mean of its divisors is an integer number (10328333259).

Almost surely, 2^20656666517 is an apocalyptic number.

It is an amenable number.

20656666517 is a deficient number, since it is larger than the sum of its proper divisors (1).

20656666517 is an equidigital number, since it uses as much as digits as its factorization.

20656666517 is an evil number, because the sum of its binary digits is even.

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

The spelling of 20656666517 in words is "twenty billion, six hundred fifty-six million, six hundred sixty-six thousand, five hundred seventeen".