20013721567517 has 2 divisors, whose sum is σ = 20013721567518. Its totient is φ = 20013721567516.

The previous prime is 20013721567409. The next prime is 20013721567559. The reversal of 20013721567517 is 71576512731002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15481502099716 + 4532219467801 = 3934654^2 + 2128901^2 .

It is a cyclic number.

It is not a de Polignac number, because 20013721567517 - 2¹⁸ = 20013721305373 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20013721567117) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10006860783758 + 10006860783759.

It is an arithmetic number, because the mean of its divisors is an integer number (10006860783759).

Almost surely, 2^{20013721567517} is an apocalyptic number.

It is an amenable number.

20013721567517 is a deficient number, since it is larger than the sum of its proper divisors (1).

20013721567517 is an equidigital number, since it uses as much as digits as its factorization.

20013721567517 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 617400, while the sum is 47.

The spelling of 20013721567517 in words is "twenty trillion, thirteen billion, seven hundred twenty-one million, five hundred sixty-seven thousand, five hundred seventeen".