25638818581 has 2 divisors, whose sum is σ = 25638818582. Its totient is φ = 25638818580.

The previous prime is 25638818551. The next prime is 25638818609. The reversal of 25638818581 is 18581883652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17540618481 + 8098200100 = 132441^2 + 89990^2 .

It is a cyclic number.

It is not a de Polignac number, because 25638818581 - 2¹⁵ = 25638785813 is a prime.

It is a super-2 number, since 2×25638818581² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25638818521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12819409290 + 12819409291.

It is an arithmetic number, because the mean of its divisors is an integer number (12819409291).

Almost surely, 2^25638818581 is an apocalyptic number.

It is an amenable number.

25638818581 is a deficient number, since it is larger than the sum of its proper divisors (1).

25638818581 is an equidigital number, since it uses as much as digits as its factorization.

25638818581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3686400, while the sum is 55.

The spelling of 25638818581 in words is "twenty-five billion, six hundred thirty-eight million, eight hundred eighteen thousand, five hundred eighty-one".