128865 has 24 divisors (see below), whose sum is σ = 229824. Its totient is φ = 61600.

The previous prime is 128861. The next prime is 128873. The reversal of 128865 is 568821.

It is not a de Polignac number, because 128865 - 2² = 128861 is a prime.

It is a Curzon number.

128865 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (128861) 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 23 ways as a sum of consecutive naturals, for example, 1780 + ... + 1850.

It is an arithmetic number, because the mean of its divisors is an integer number (9576).

2¹²⁸⁸⁶⁵ is an apocalyptic number.

128865 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

128865 is a deficient number, since it is larger than the sum of its proper divisors (100959).

128865 is a wasteful number, since it uses less digits than its factorization.

128865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101 (or 90 counting only the distinct ones).

The product of its digits is 3840, while the sum is 30.

The square root of 128865 is about 358.9777151858. The cubic root of 128865 is about 50.5101113629.

The spelling of 128865 in words is "one hundred twenty-eight thousand, eight hundred sixty-five".