18539581609 has 2 divisors, whose sum is σ = 18539581610. Its totient is φ = 18539581608.

The previous prime is 18539581561. The next prime is 18539581649. The reversal of 18539581609 is 90618593581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14964139584 + 3575442025 = 122328^2 + 59795^2 .

It is a cyclic number.

It is not a de Polignac number, because 18539581609 - 2⁷ = 18539581481 is a prime.

It is a super-4 number, since 4×18539581609⁴ (a number of 42 digits) contains 4444 as substring. Note that it is a super-d number also for d = 3.

It is a self number, because there is not a number n which added to its sum of digits gives 18539581609.

It is not a weakly prime, because it can be changed into another prime (18539581649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9269790804 + 9269790805.

It is an arithmetic number, because the mean of its divisors is an integer number (9269790805).

Almost surely, 2^18539581609 is an apocalyptic number.

It is an amenable number.

18539581609 is a deficient number, since it is larger than the sum of its proper divisors (1).

18539581609 is an equidigital number, since it uses as much as digits as its factorization.

18539581609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2332800, while the sum is 55.

The spelling of 18539581609 in words is "eighteen billion, five hundred thirty-nine million, five hundred eighty-one thousand, six hundred nine".