freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/project-euler/problem-153-investigating-gaussian-integers.english.md

---
id: 5900f4051000cf542c50ff18
challengeType: 5
title: 'Problem 153: Investigating Gaussian Integers'
---

## Description
<section id='description'>
As we all know the equation x2=-1 has no solutions for real x.

If we however introduce the imaginary number i this equation has two solutions: x=i and x=-i.

If we go a step further the equation (x-3)2=-4 has two complex solutions: x=3+2i and x=3-2i.
x=3+2i and x=3-2i are called each others' complex conjugate.

Numbers of the form a+bi are called complex numbers.

In general a+bi and a−bi are each other's complex conjugate.
A Gaussian Integer is a complex number a+bi such that both a and b are integers.

The regular integers are also Gaussian integers (with b=0).

To distinguish them from Gaussian integers with b ≠ 0 we call such integers "rational integers."

A Gaussian integer is called a divisor of a rational integer n if the result is also a Gaussian integer.

If for example we divide 5 by 1+2i we can simplify  in the following manner:

Multiply numerator and denominator by the complex conjugate of 1+2i: 1−2i.

The result is
.

So 1+2i is a divisor of 5.

Note that 1+i is not a divisor of 5 because .

Note also that if the Gaussian Integer (a+bi) is a divisor of a rational integer n, then its complex conjugate (a−bi) is also a divisor of n.
In fact, 5 has six divisors such that the real part is positive: {1, 1 + 2i, 1 − 2i, 2 + i, 2 − i, 5}.

The following is a table of all of the divisors for the first five positive rational integers:

n Gaussian integer divisors
with positive real partSum s(n) of these

divisors111
21, 1+i, 1-i, 25
31, 34
41, 1+i, 1-i, 2, 2+2i, 2-2i,413
51, 1+2i, 1-2i, 2+i, 2-i, 512
For divisors with positive real parts, then, we have: .
For 1 ≤ n ≤ 105, ∑ s(n)=17924657155.
What is ∑ s(n) for 1 ≤ n ≤ 108?
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler153()</code> should return 17971254122360636.
    testString: assert.strictEqual(euler153(), 17971254122360636, '<code>euler153()</code> should return 17971254122360636.');

```

</section>

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

<div id='js-seed'>

```js
function euler153() {
  // Good luck!
  return true;
}

euler153();
```

</div>



</section>

## Solution
<section id='solution'>

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