Addition · Grades 4–7 · Unsolved

The 196 Problem

Reverse a number and add. Repeat until it reads the same both ways. Does 196 ever get there?

How many steps each starting number from 10 to 199 needs. Most need one or two. 196 has never finished.

Try it

57 + 75 = 132132 + 231 = 363 ✓196 + 691 = 887…

Computers have followed 196 for hundreds of millions of digits. Still no palindrome.

Nobody has proved that any number never gets there.

Which two-digit numbers finish in one step? Why those?

89 and 98 take the same number of steps. Why?

Detailed one-pager (PDF) History, why it’s unsolved, and more classroom ideas