128409 has 8 divisors (see below), whose sum is σ = 178752. Its totient is φ = 81840.

The previous prime is 128399. The next prime is 128411. The reversal of 128409 is 904821.

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

It is not a de Polignac number, because 128409 - 2⁴ = 128393 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

128409 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (128449) 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 7 ways as a sum of consecutive naturals, for example, 862 + ... + 999.

It is an arithmetic number, because the mean of its divisors is an integer number (22344).

2¹²⁸⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

128409 is a deficient number, since it is larger than the sum of its proper divisors (50343).

128409 is a wasteful number, since it uses less digits than its factorization.

128409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1887.

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 128409 is about 358.3420153987. The cubic root of 128409 is about 50.4504628109.

The spelling of 128409 in words is "one hundred twenty-eight thousand, four hundred nine".