freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-129-repunit-divisibility.english.md

---
id: 5900f3ef1000cf542c50ff01
challengeType: 5
title: 'Problem 129: Repunit divisibility'
---

## 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.
Given that n is a positive integer and GCD(n, 10) = 1, it can be shown that there always exists a value, k, for which R(k) is divisible by n, and let A(n) be the least such value of k; for example, A(7) = 6 and A(41) = 5.
The least value of n for which A(n) first exceeds ten is 17.
Find the least value of n for which A(n) first exceeds one-million.
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler129()</code> should return 1000023.
    testString: assert.strictEqual(euler129(), 1000023, '<code>euler129()</code> should return 1000023.');

```

</section>

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

<div id='js-seed'>

```js
function euler129() {
  // Good luck!
  return true;
}

euler129();
```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```
</section>