20505385517 has 2 divisors, whose sum is σ = 20505385518. Its totient is φ = 20505385516.

The previous prime is 20505385469. The next prime is 20505385529. The reversal of 20505385517 is 71558350502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10495182916 + 10010202601 = 102446^2 + 100051^2 .

It is a cyclic number.

It is not a de Polignac number, because 20505385517 - 2²⁶ = 20438276653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20505385217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10252692758 + 10252692759.

It is an arithmetic number, because the mean of its divisors is an integer number (10252692759).

Almost surely, 2^20505385517 is an apocalyptic number.

It is an amenable number.

20505385517 is a deficient number, since it is larger than the sum of its proper divisors (1).

20505385517 is an equidigital number, since it uses as much as digits as its factorization.

20505385517 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 210000, while the sum is 41.

The spelling of 20505385517 in words is "twenty billion, five hundred five million, three hundred eighty-five thousand, five hundred seventeen".