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How Many 3-Digit Palindromes Are Divisible by 11?

Published in Number Theory 2 mins read

There are eight 3-digit palindromes divisible by 11.

Understanding Palindromes and Divisibility by 11

A palindrome is a number that remains the same when its digits are reversed. A three-digit palindrome has the form ABA, where A and B are digits from 0 to 9, and A cannot be 0. Divisibility by 11 means that the number is perfectly divisible by 11 without leaving a remainder.

While not all palindromes are divisible by 11, there's a pattern for those with an even number of digits: they are always divisible by 11. However, this rule doesn't apply to palindromes with an odd number of digits, like our three-digit case.

Finding the 3-Digit Palindromes Divisible by 11

Let's list them:

  • 121
  • 242
  • 363
  • 484
  • 616
  • 737
  • 858
  • 979

These are all the three-digit palindromes that are divisible by 11. You can verify this by performing the division for each number.

A Note on Other Digit Palindromes

It's important to note that the divisibility rule by 11 changes based on the number of digits. For example:

  • Even-digit palindromes: Always divisible by 11.
  • Odd-digit palindromes: Not always divisible by 11; the divisibility depends on the specific digits.

This information clarifies why there are only eight three-digit palindromes fitting our criteria.

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