128009 has 4 divisors (see below), whose sum is σ = 146304. Its totient is φ = 109716.

The previous prime is 127997. The next prime is 128021. The reversal of 128009 is 900821.

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 an interprime number because it is at equal distance from previous prime (127997) and next prime (128021).

It is a cyclic number.

It is not a de Polignac number, because 128009 - 2¹⁶ = 62473 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (128099) 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, 9137 + ... + 9150.

It is an arithmetic number, because the mean of its divisors is an integer number (36576).

2¹²⁸⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

128009 is a deficient number, since it is larger than the sum of its proper divisors (18295).

128009 is an equidigital number, since it uses as much as digits as its factorization.

128009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18294.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 128009 is about 357.7834540613. The cubic root of 128009 is about 50.3980231441.

The spelling of 128009 in words is "one hundred twenty-eight thousand, nine".