---
id: 5900f3f21000cf542c50ff04
challengeType: 5
title: 'Problem 133: Repunit nonfactors'
---
## Description
A number consisting entirely of ones is called a repunit. We shall define R(k) to be a repunit of length k; for example, R(6) = 111111.
Let us consider repunits of the form R(10n).
Although R(10), R(100), or R(1000) are not divisible by 17, R(10000) is divisible by 17. Yet there is no value of n for which R(10n) will divide by 19. In fact, it is remarkable that 11, 17, 41, and 73 are the only four primes below one-hundred that can be a factor of R(10n).
Find the sum of all the primes below one-hundred thousand that will never be a factor of R(10n).
## Instructions
## Tests
```yml
tests:
- text: euler133() should return 453647705.
testString: assert.strictEqual(euler133(), 453647705, 'euler133() should return 453647705.');
```
## Challenge Seed
```js
function euler133() {
// Good luck!
return true;
}
euler133();
```