128909 has 4 divisors (see below), whose sum is σ = 140640. Its totient is φ = 117180.

The previous prime is 128903. The next prime is 128923. The reversal of 128909 is 909821.

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 a de Polignac number, because none of the positive numbers 2^k-128909 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 (128903) 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, 5849 + ... + 5870.

It is an arithmetic number, because the mean of its divisors is an integer number (35160).

2¹²⁸⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

128909 is a deficient number, since it is larger than the sum of its proper divisors (11731).

128909 is a wasteful number, since it uses less digits than its factorization.

128909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11730.

The product of its (nonzero) digits is 1296, while the sum is 29.

The square root of 128909 is about 359.0389950966. The cubic root of 128909 is about 50.5158594766.

The spelling of 128909 in words is "one hundred twenty-eight thousand, nine hundred nine".