Medium
Enter a number above and click "Reveal Solution"
to watch the steps appear — written by hand.
to watch the steps appear — written by hand.
About this conjecture
The Rules
Two simple rules
If your number is even, divide it by 2.
If your number is odd, multiply by 3 and add 1.
Repeat until you reach 1.
The Mystery
Unsolved since 1937
Proposed by Lothar Collatz, this conjecture has been tested for every number up to 268 — and it always works. Yet no one has proven it must work for every number.
Try These
Fun numbers to test
27 → 111 steps, peaks at 9,232
871 → 178 steps, peaks at 190,996
6 → just 8 steps — simple!
703 → 170 steps — a wild ride