25518521081 has 2 divisors, whose sum is σ = 25518521082. Its totient is φ = 25518521080.

The previous prime is 25518521051. The next prime is 25518521117. The reversal of 25518521081 is 18012581552.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 25501215481 + 17305600 = 159691^2 + 4160^2 .

It is a cyclic number.

It is not a de Polignac number, because 25518521081 - 2²² = 25514326777 is a prime.

It is a super-2 number, since 2×25518521081² (a number of 22 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (25518521051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12759260540 + 12759260541.

It is an arithmetic number, because the mean of its divisors is an integer number (12759260541).

Almost surely, 2^25518521081 is an apocalyptic number.

It is an amenable number.

25518521081 is a deficient number, since it is larger than the sum of its proper divisors (1).

25518521081 is an equidigital number, since it uses as much as digits as its factorization.

25518521081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32000, while the sum is 38.

The spelling of 25518521081 in words is "twenty-five billion, five hundred eighteen million, five hundred twenty-one thousand, eighty-one".