18511866509 has 2 divisors, whose sum is σ = 18511866510. Its totient is φ = 18511866508.

The previous prime is 18511866427. The next prime is 18511866517. The reversal of 18511866509 is 90566811581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18276336100 + 235530409 = 135190^2 + 15347^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18511866509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18511866539) 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, 9255933254 + 9255933255.

It is an arithmetic number, because the mean of its divisors is an integer number (9255933255).

Almost surely, 2^18511866509 is an apocalyptic number.

It is an amenable number.

18511866509 is a deficient number, since it is larger than the sum of its proper divisors (1).

18511866509 is an equidigital number, since it uses as much as digits as its factorization.

18511866509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 518400, while the sum is 50.

The spelling of 18511866509 in words is "eighteen billion, five hundred eleven million, eight hundred sixty-six thousand, five hundred nine".