freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-129-repunit-divisibility.md

---
id: 5900f3ef1000cf542c50ff01
title: 'Problem 129: Repunit divisibility'
challengeType: 5
forumTopicId: 301756
dashedName: problem-129-repunit-divisibility
---

# --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.

# --hints--

`euler129()` should return 1000023.

```js
assert.strictEqual(euler129(), 1000023);
```

# --seed--

## --seed-contents--

```js
function euler129() {

  return true;
}

euler129();
```

# --solutions--

```js
// solution required
```