18381557317 has 4 divisors (see below), whose sum is σ = 18563553036. Its totient is φ = 18199561600.

The previous prime is 18381557297. The next prime is 18381557323. The reversal of 18381557317 is 71375518381.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10186057476 + 8195499841 = 100926^2 + 90529^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18381557317 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18381557617) 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, 90997708 + ... + 90997909.

It is an arithmetic number, because the mean of its divisors is an integer number (4640888259).

Almost surely, 2^18381557317 is an apocalyptic number.

It is an amenable number.

18381557317 is a deficient number, since it is larger than the sum of its proper divisors (181995719).

18381557317 is a wasteful number, since it uses less digits than its factorization.

18381557317 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181995718.

The product of its digits is 705600, while the sum is 49.

The spelling of 18381557317 in words is "eighteen billion, three hundred eighty-one million, five hundred fifty-seven thousand, three hundred seventeen".