128665109 has 4 divisors (see below), whose sum is σ = 129140160. Its totient is φ = 128190060.

The previous prime is 128665099. The next prime is 128665127. The reversal of 128665109 is 901566821.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 128665109 - 2⁸ = 128664853 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128665309) 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, 237119 + ... + 237660.

It is an arithmetic number, because the mean of its divisors is an integer number (32285040).

Almost surely, 2^128665109 is an apocalyptic number.

It is an amenable number.

128665109 is a deficient number, since it is larger than the sum of its proper divisors (475051).

128665109 is an equidigital number, since it uses as much as digits as its factorization.

128665109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 475050.

The product of its (nonzero) digits is 25920, while the sum is 38.

The square root of 128665109 is about 11343.0643566895. The cubic root of 128665109 is about 504.8398132595.

The spelling of 128665109 in words is "one hundred twenty-eight million, six hundred sixty-five thousand, one hundred nine".