Sunday Times Teaser 2963 – A Result
by Graham Smithers
Published July 7 2019 (link)
For any number, I square the digits and then add the resulting numbers. If necessary, I keep repeating the process until I end up with a single digit, called the result.
For example: 142 gives 1 + 16 + 4 = 21 which then gives 4 + 1 = 5, the result. I have written down a two-digit number.
If I tell you one of the digits [the key digit], you should be able to work out the result.
I then use a 3rd digit to get a three-digit number. The result of that number happens to be the key digit.
In increasing order, what are the three digits?