25544644561 has 2 divisors, whose sum is σ = 25544644562. Its totient is φ = 25544644560.

The previous prime is 25544644507. The next prime is 25544644589. The reversal of 25544644561 is 16544644552.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 24256193536 + 1288451025 = 155744^2 + 35895^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-25544644561 is a prime.

It is not a weakly prime, because it can be changed into another prime (25544644591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12772322280 + 12772322281.

It is an arithmetic number, because the mean of its divisors is an integer number (12772322281).

Almost surely, 2^25544644561 is an apocalyptic number.

It is an amenable number.

25544644561 is a deficient number, since it is larger than the sum of its proper divisors (1).

25544644561 is an equidigital number, since it uses as much as digits as its factorization.

25544644561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2304000, while the sum is 46.

Subtracting from 25544644561 its reverse (16544644552), we obtain a palindrome (9000000009).

The spelling of 25544644561 in words is "twenty-five billion, five hundred forty-four million, six hundred forty-four thousand, five hundred sixty-one".