128005 has 4 divisors (see below), whose sum is σ = 153612. Its totient is φ = 102400.

The previous prime is 127997. The next prime is 128021. The reversal of 128005 is 500821.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 101761 + 26244 = 319^2 + 162^2 .

It is not a de Polignac number, because 128005 - 2³ = 127997 is a prime.

It is a Duffinian number.

128005 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 128005.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12796 + ... + 12805.

It is an arithmetic number, because the mean of its divisors is an integer number (38403).

2¹²⁸⁰⁰⁵ is an apocalyptic number.

It is an amenable number.

128005 is a deficient number, since it is larger than the sum of its proper divisors (25607).

128005 is an equidigital number, since it uses as much as digits as its factorization.

128005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25606.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 128005 is about 357.7778640442. Note that the first 3 decimals coincide. The cubic root of 128005 is about 50.3974981961.

Adding to 128005 its reverse (500821), we get a palindrome (628826).

Subtracting 128005 from its reverse (500821), we obtain a triangular number (372816 = T₈₆₃).

It can be divided in two parts, 12800 and 5, that multiplied together give a cube (64000 = 40³).

The spelling of 128005 in words is "one hundred twenty-eight thousand, five".