2565251721 has 8 divisors (see below), whose sum is σ = 3800372960. Its totient is φ = 1710167796.

The previous prime is 2565251683. The next prime is 2565251723. The reversal of 2565251721 is 1271525652.

2565251721 is a `hidden beast` number, since 2 + 565 + 25 + 1 + 72 + 1 = 666.

It is not a de Polignac number, because 2565251721 - 2⁶ = 2565251657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2565251723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 47504635 + ... + 47504688.

It is an arithmetic number, because the mean of its divisors is an integer number (475046620).

Almost surely, 2^2565251721 is an apocalyptic number.

It is an amenable number.

2565251721 is a deficient number, since it is larger than the sum of its proper divisors (1235121239).

2565251721 is an equidigital number, since it uses as much as digits as its factorization.

2565251721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95009332 (or 95009326 counting only the distinct ones).

The product of its digits is 42000, while the sum is 36.

The square root of 2565251721 is about 50648.3140982995. The cubic root of 2565251721 is about 1368.9155680369.

The spelling of 2565251721 in words is "two billion, five hundred sixty-five million, two hundred fifty-one thousand, seven hundred twenty-one".