25511516561 has 4 divisors (see below), whose sum is σ = 25512373824. Its totient is φ = 25510659300.

The previous prime is 25511516549. The next prime is 25511516587. The reversal of 25511516561 is 16561511552.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-25511516561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (25511516521) 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, 382325 + ... + 444066.

It is an arithmetic number, because the mean of its divisors is an integer number (6378093456).

Almost surely, 2^25511516561 is an apocalyptic number.

It is an amenable number.

25511516561 is a deficient number, since it is larger than the sum of its proper divisors (857263).

25511516561 is an equidigital number, since it uses as much as digits as its factorization.

25511516561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 857262.

The product of its digits is 45000, while the sum is 38.

The spelling of 25511516561 in words is "twenty-five billion, five hundred eleven million, five hundred sixteen thousand, five hundred sixty-one".