freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-429-sum-of-squares-of-unitary-divisors.english.md

---
id: 5900f5191000cf542c51002c
challengeType: 5
title: 'Problem 429: Sum of squares of unitary divisors'
---

## Description
<section id='description'>
A unitary divisor d of a number n is a divisor of n that has the property gcd(d, n/d) = 1.
The unitary divisors of 4! = 24 are 1, 3, 8 and 24.
The sum of their squares is 12 + 32 + 82 + 242 = 650.


Let S(n) represent the sum of the squares of the unitary divisors of n. Thus S(4!)=650.


Find S(100 000 000!) modulo 1 000 000 009.
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler429()</code> should return 98792821.
    testString: assert.strictEqual(euler429(), 98792821, '<code>euler429()</code> should return 98792821.');

```

</section>

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

<div id='js-seed'>

```js
function euler429() {
  // Good luck!
  return true;
}

euler429();
```

</div>



</section>

## Solution
<section id='solution'>

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