2661256516165 has 16 divisors (see below), whose sum is σ = 3464265652848. Its totient is φ = 1950890789376.

The previous prime is 2661256516129. The next prime is 2661256516169. The reversal of 2661256516165 is 5616156521662.

It can be written as a sum of positive squares in 8 ways, for example, as 344191075684 + 2317065440481 = 586678^2 + 1522191^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2661256516165 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2661256516169) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 149415942 + ... + 149433751.

It is an arithmetic number, because the mean of its divisors is an integer number (216516603303).

Almost surely, 2^{2661256516165} is an apocalyptic number.

It is an amenable number.

2661256516165 is a deficient number, since it is larger than the sum of its proper divisors (803009136683).

2661256516165 is a wasteful number, since it uses less digits than its factorization.

2661256516165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 298849848.

The product of its digits is 3888000, while the sum is 52.

The spelling of 2661256516165 in words is "two trillion, six hundred sixty-one billion, two hundred fifty-six million, five hundred sixteen thousand, one hundred sixty-five".