freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-133-repunit-nonfactors.english.md

---
id: 5900f3f21000cf542c50ff04
challengeType: 5
title: 'Problem 133: Repunit nonfactors'
---

## Description
<section id='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).
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler133()</code> should return 453647705.
    testString: assert.strictEqual(euler133(), 453647705);

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
function euler133() {
  // Good luck!
  return true;
}

euler133();
```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```

</section>