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freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-429-sum-of-squares-of-unitary-divisors.english.md
Oliver Eyton-Williams bd68b70f3d Feat: hide blocks not challenges (#39504)
* fix: remove isHidden flag from frontmatter

* fix: add isUpcomingChange

Co-authored-by: Ahmad Abdolsaheb <ahmad.abdolsaheb@gmail.com>

* feat: hide blocks not challenges

Co-authored-by: Ahmad Abdolsaheb <ahmad.abdolsaheb@gmail.com>

Co-authored-by: Ahmad Abdolsaheb <ahmad.abdolsaheb@gmail.com>
2020-09-03 15:07:40 -07:00

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---
id: 5900f5191000cf542c51002c
challengeType: 5
title: 'Problem 429: Sum of squares of unitary divisors'
forumTopicId: 302099
---
## 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);
```
</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>