2561665263 has 16 divisors (see below), whose sum is σ = 3435803136. Its totient is φ = 1697675840.

The previous prime is 2561665259. The next prime is 2561665313. The reversal of 2561665263 is 3625661652.

It is a cyclic number.

It is not a de Polignac number, because 2561665263 - 2² = 2561665259 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2561665163) 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, 515770 + ... + 520712.

It is an arithmetic number, because the mean of its divisors is an integer number (214737696).

Almost surely, 2^2561665263 is an apocalyptic number.

2561665263 is a deficient number, since it is larger than the sum of its proper divisors (874137873).

2561665263 is a wasteful number, since it uses less digits than its factorization.

2561665263 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5934.

The product of its digits is 388800, while the sum is 42.

The square root of 2561665263 is about 50612.8962123291. The cubic root of 2561665263 is about 1368.2773138474.

The spelling of 2561665263 in words is "two billion, five hundred sixty-one million, six hundred sixty-five thousand, two hundred sixty-three".