
Square digit chains
Problem 92
Published on Friday, 1st April 2005, 06:00 pm; Solved by 19600A 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?