freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-133-repunit-nonfactors.md

---
id: 5900f3f21000cf542c50ff04
title: 'Problem 133: Repunit nonfactors'
challengeType: 5
forumTopicId: 301761
---

# --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).

# --hints--

`euler133()` should return 453647705.

```js
assert.strictEqual(euler133(), 453647705);
```

# --seed--

## --seed-contents--

```js
function euler133() {

  return true;
}

euler133();
```

# --solutions--

```js
// solution required
```