1561720516117 has 2 divisors, whose sum is σ = 1561720516118. Its totient is φ = 1561720516116.

The previous prime is 1561720516099. The next prime is 1561720516123. The reversal of 1561720516117 is 7116150271651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1561115306916 + 605209201 = 1249446^2 + 24601^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561720516117 - 2¹⁹ = 1561719991829 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1561720516417) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780860258058 + 780860258059.

It is an arithmetic number, because the mean of its divisors is an integer number (780860258059).

Almost surely, 2^{1561720516117} is an apocalyptic number.

It is an amenable number.

1561720516117 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561720516117 is an equidigital number, since it uses as much as digits as its factorization.

1561720516117 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 88200, while the sum is 43.

Adding to 1561720516117 its reverse (7116150271651), we get a palindrome (8677870787768).

The spelling of 1561720516117 in words is "one trillion, five hundred sixty-one billion, seven hundred twenty million, five hundred sixteen thousand, one hundred seventeen".