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The Kaprekar Number
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The Kaprekar Number is 6174.
(1) Take any four-digit number.
(2) Form the largest and the smallest numbers from these four digits.
(3) Find the difference between those digits. Maybe this is 6174.
If it is not, form the largest and the smallest number
from the difference and subtract these numbers again.
You may have to repeat this procedure.
The end result is always 6174, with no more than 7 steps.
For example, take the number 3546.
1st step: 6543 - 3456 = 3087
2nd step: 8730 - 0378 = 8352
3rd step: 8532 - 2358 = 6174
Or, take the number 5184.
1st step: 8541 - 1458 = 7083
2nd step: 8730 - 0378 = 8532
3rd step: 8532 - 2358 = 6174
Notice the final result is always 6174. Why?

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