2565681521 has 4 divisors (see below), whose sum is σ = 2763041652. Its totient is φ = 2368321392.

The previous prime is 2565681479. The next prime is 2565681529. The reversal of 2565681521 is 1251865652.

2565681521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It can be written as a sum of positive squares in 2 ways, for example, as 334158400 + 2231523121 = 18280^2 + 47239^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2565681521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2565681529) 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, 98680046 + ... + 98680071.

It is an arithmetic number, because the mean of its divisors is an integer number (690760413).

Almost surely, 2^2565681521 is an apocalyptic number.

It is an amenable number.

2565681521 is a deficient number, since it is larger than the sum of its proper divisors (197360131).

2565681521 is a wasteful number, since it uses less digits than its factorization.

2565681521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197360130.

The product of its digits is 144000, while the sum is 41.

The square root of 2565681521 is about 50652.5569048592. The cubic root of 2565681521 is about 1368.9920162921.

The spelling of 2565681521 in words is "two billion, five hundred sixty-five million, six hundred eighty-one thousand, five hundred twenty-one".