About Kaprekar’s Constant
Kaprekar’s constant is a mathematical curiosity: take any four-digit number with at least two different digits, rearrange and subtract, and you will always land on 6174 within seven steps.
Discovered by the Indian mathematician D. R. Kaprekar in 1949, this quirk of arithmetic has fascinated mathematicians and recreational puzzle enthusiasts ever since. Every valid four-digit starting number reaches 6174 within seven iterations, and once it arrives, it stays there forever.
Try it yourself on the interactive solver, or read the step-by-step explanation, browse worked examples, or dig into the mathematics behind it. For three-digit numbers, there is an analogous constant: 495.