freeCodeCamp/curriculum/challenges/chinese/10-coding-interview-prep/project-euler/problem-401-sum-of-squares-of-divisors.md

---
id: 5900f4fd1000cf542c51000f
title: 'Problem 401: Sum of squares of divisors'
challengeType: 5
forumTopicId: 302069
dashedName: problem-401-sum-of-squares-of-divisors
---

# --description--

The divisors of 6 are 1,2,3 and 6.

The sum of the squares of these numbers is 1+4+9+36=50.

Let sigma2(n) represent the sum of the squares of the divisors of n. Thus sigma2(6)=50.

Let SIGMA2 represent the summatory function of sigma2, that is SIGMA2(n)=∑sigma2(i) for i=1 to n. The first 6 values of SIGMA2 are: 1,6,16,37,63 and 113.

Find SIGMA2(1015) modulo 109.

# --hints--

`euler401()` should return 281632621.

```js
assert.strictEqual(euler401(), 281632621);
```

# --seed--

## --seed-contents--

```js
function euler401() {

  return true;
}

euler401();
```

# --solutions--

```js
// solution required
```