18510981865 has 4 divisors (see below), whose sum is σ = 22213178244. Its totient is φ = 14808785488.

The previous prime is 18510981833. The next prime is 18510981961. The reversal of 18510981865 is 56818901581.

It is a happy number.

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 7243371664 + 11267610201 = 85108^2 + 106149^2 .

It is a cyclic number.

It is not a de Polignac number, because 18510981865 - 2⁵ = 18510981833 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1851098182 + ... + 1851098191.

It is an arithmetic number, because the mean of its divisors is an integer number (5553294561).

Almost surely, 2^18510981865 is an apocalyptic number.

It is an amenable number.

18510981865 is a deficient number, since it is larger than the sum of its proper divisors (3702196379).

18510981865 is an equidigital number, since it uses as much as digits as its factorization.

18510981865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3702196378.

The product of its (nonzero) digits is 691200, while the sum is 52.

The spelling of 18510981865 in words is "eighteen billion, five hundred ten million, nine hundred eighty-one thousand, eight hundred sixty-five".