128309 has 4 divisors (see below), whose sum is σ = 132480. Its totient is φ = 124140.

The previous prime is 128291. The next prime is 128311. The reversal of 128309 is 903821.

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, and also an emirpimes, since its reverse is a distinct semiprime: 903821 = 59 ⋅15319.

It is a cyclic number.

It is not a de Polignac number, because 128309 - 2⁸ = 128053 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 (128339) 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, 2039 + ... + 2100.

It is an arithmetic number, because the mean of its divisors is an integer number (33120).

2¹²⁸³⁰⁹ is an apocalyptic number.

It is an amenable number.

128309 is a deficient number, since it is larger than the sum of its proper divisors (4171).

128309 is an equidigital number, since it uses as much as digits as its factorization.

128309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4170.

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 128309 is about 358.2024567197. The cubic root of 128309 is about 50.4373631152.

The spelling of 128309 in words is "one hundred twenty-eight thousand, three hundred nine".