freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-171-finding-numbers-for-which-the-sum-of-the-squares-of-the-digits-is-a-square.md

id	title	challengeType	forumTopicId	dashedName
5900f4181000cf542c50ff2a	Problem 171: Finding numbers for which the sum of the squares of the digits is a square	5	301806	problem-171-finding-numbers-for-which-the-sum-of-the-squares-of-the-digits-is-a-square

--description--

For a positive integer n, let f(n) be the sum of the squares of the digits (in base 10) of n, e.g.

\begin{align}
  & f(3) = 3^2 = 9 \\\\
  & f(25) = 2^2 + 5^2 = 4 + 25 = 29 \\\\
  & f(442) = 4^2 + 4^2 + 2^2 = 16 + 16 + 4 = 36 \\\\
\end{align}$$

Find the last nine digits of the sum of all $n$, $0 < n < {10}^{20}$, such that $f(n)$ is a perfect square.

# --hints--

`lastDigitsSumOfPerfectSquare()` should return `142989277`.

```js
assert.strictEqual(lastDigitsSumOfPerfectSquare(), 142989277);
```

# --seed--

## --seed-contents--

```js
function lastDigitsSumOfPerfectSquare() {

  return true;
}

lastDigitsSumOfPerfectSquare();
```

# --solutions--

```js
// solution required
```