2565918991 has 4 divisors (see below), whose sum is σ = 2582911984. Its totient is φ = 2548926000.

The previous prime is 2565918989. The next prime is 2565919001. The reversal of 2565918991 is 1998195652.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 2565918991 - 2¹ = 2565918989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2565918941) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8496270 + ... + 8496571.

It is an arithmetic number, because the mean of its divisors is an integer number (645727996).

Almost surely, 2^2565918991 is an apocalyptic number.

2565918991 is a deficient number, since it is larger than the sum of its proper divisors (16992993).

2565918991 is a wasteful number, since it uses less digits than its factorization.

2565918991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16992992.

The product of its digits is 1749600, while the sum is 55.

The square root of 2565918991 is about 50654.9009573605. The cubic root of 2565918991 is about 1369.0342512697.

The spelling of 2565918991 in words is "two billion, five hundred sixty-five million, nine hundred eighteen thousand, nine hundred ninety-one".