18128809 has 8 divisors (see below), whose sum is σ = 18538632. Its totient is φ = 17721600.

The previous prime is 18128801. The next prime is 18128813. The reversal of 18128809 is 90882181.

It can be written as a sum of positive squares in 4 ways, for example, as 5419584 + 12709225 = 2328^2 + 3565^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18128809 - 2³ = 18128801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18128801) 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 in 7 ways as a sum of consecutive naturals, for example, 20827 + ... + 21679.

It is an arithmetic number, because the mean of its divisors is an integer number (2317329).

Almost surely, 2^18128809 is an apocalyptic number.

It is an amenable number.

18128809 is a deficient number, since it is larger than the sum of its proper divisors (409823).

18128809 is an equidigital number, since it uses as much as digits as its factorization.

18128809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1307.

The product of its (nonzero) digits is 9216, while the sum is 37.

The square root of 18128809 is about 4257.7939123447. The cubic root of 18128809 is about 262.6977931783.

The spelling of 18128809 in words is "eighteen million, one hundred twenty-eight thousand, eight hundred nine".