2661256516129 has 2 divisors, whose sum is σ = 2661256516130. Its totient is φ = 2661256516128.

The previous prime is 2661256516111. The next prime is 2661256516169. The reversal of 2661256516129 is 9216156521662.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2046765145104 + 614491371025 = 1430652^2 + 783895^2 .

It is a cyclic number.

It is not a de Polignac number, because 2661256516129 - 2³⁷ = 2523817562657 is a prime.

It is not a weakly prime, because it can be changed into another prime (2661256516169) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1330628258064 + 1330628258065.

It is an arithmetic number, because the mean of its divisors is an integer number (1330628258065).

Almost surely, 2^{2661256516129} is an apocalyptic number.

It is an amenable number.

2661256516129 is a deficient number, since it is larger than the sum of its proper divisors (1).

2661256516129 is an equidigital number, since it uses as much as digits as its factorization.

2661256516129 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2332800, while the sum is 52.

The spelling of 2661256516129 in words is "two trillion, six hundred sixty-one billion, two hundred fifty-six million, five hundred sixteen thousand, one hundred twenty-nine".