How many different palindromes are there with 6 digits?

Answer 1

For there to be palindromes, each digit must be replicated. Therefore there are at most three distinct digits.

If there are 3 pairs of different digits, then there are 6 palindromes. If there can be more duplicate digits, then there are 27 palindromes.

Answer 2

There are 900 six-digit palindromes.