---
id: 5900f3c81000cf542c50fedb
challengeType: 5
title: 'Problem 92: Square digit chains'
forumTopicId: 302209
---
## Description
A number chain is created by continuously adding the square of the digits in a number to form a new number until it has been seen before.
For example,
44 → 32 → 13 → 10 → 1 → 1
85 → 89 → 145 → 42 → 20 → 4 → 16 → 37 → 58 → 89
Therefore any chain that arrives at 1 or 89 will become stuck in an endless loop. What is most amazing is that EVERY starting number will eventually arrive at 1 or 89.
How many starting numbers below ten million will arrive at 89?
## Instructions
## Tests
```yml
tests:
- text: squareDigitChains() should return a number.
testString: assert(typeof squareDigitChains() === 'number');
- text: squareDigitChains() should return 8581146.
testString: assert.strictEqual(squareDigitChains(), 8581146);
```
## Challenge Seed
```js
function squareDigitChains() {
return true;
}
squareDigitChains();
```
## Solution
```js
// solution required
```