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A number is called swappy if it is not a palindrome, but swapping two of its digits produces a six-digit palindrome. For example, the number 813381 is swappy, because we can swap the last two digits to get 813318, which is a palindrome.

How many swappy six-digit numbers are there?

 Feb 22, 2020
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There are: 810 "Swappy Numbers" if you count the 90 palindromes that are already there. If you don't wish to include them, then you have: 810 - 90 =720 "Swappy Numbers"

 Feb 22, 2020

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