---
id: 5900f5041000cf542c510016
challengeType: 5
title: 'Problem 407: Idempotents'
videoUrl: ''
localeTitle: 'Problema 407: Idempotents'
---

## Description
<section id="description"> Se calcularmos a2 mod 6 para 0 ≤ a ≤ 5 obtemos: 0,1,4,3,4,1. <p> O maior valor de um tal que a2 ≡ um mod 6 é 4. Vamos chamar M (n) o maior valor de um &lt;n tal que a2 ≡ a (mod n). Então M (6) = 4. </p><p> Encontre ∑M (n) para 1 ≤ n ≤ 107. </p></section>

## Instructions
<section id="instructions">
</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler407()</code> deve retornar 39782849136421.
    testString: 'assert.strictEqual(euler407(), 39782849136421, "<code>euler407()</code> should return 39782849136421.");'

```

</section>

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

<div id='js-seed'>

```js
function euler407() {
  // Good luck!
  return true;
}

euler407();

```

</div>



</section>

## Solution
<section id='solution'>

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