128809 has 4 divisors (see below), whose sum is σ = 136404. Its totient is φ = 121216.

The previous prime is 128767. The next prime is 128813. The reversal of 128809 is 908821.

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 38809 + 90000 = 197^2 + 300^2 .

It is a cyclic number.

It is not a de Polignac number, because 128809 - 2¹¹ = 126761 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (128819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3772 + ... + 3805.

It is an arithmetic number, because the mean of its divisors is an integer number (34101).

2¹²⁸⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

128809 is a deficient number, since it is larger than the sum of its proper divisors (7595).

128809 is an equidigital number, since it uses as much as digits as its factorization.

128809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7594.

The product of its (nonzero) digits is 1152, while the sum is 28.

The square root of 128809 is about 358.8997074393. The cubic root of 128809 is about 50.5027936892.

The spelling of 128809 in words is "one hundred twenty-eight thousand, eight hundred nine".