1001 - 1991, etc = 10, x (2,3,4,5,6,7,8,9) 8 = 80
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Oh, dude, palindromic numbers are like those cool numbers that read the same forwards and backwards, right? So, between 1000 and 10000, you've got numbers like 1001, 1111, 1221... and so on. There are like 90 of them in total. So, like, that's your answer.
There are more 12-digit palindromic numbers than 11-digit palindromic numbers. This is because the number of possible 12-digit palindromic numbers is greater than the number of possible 11-digit palindromic numbers. In general, the number of palindromic numbers of length n is 9 * 10^((n-1)/2), so for 11-digit palindromic numbers, there are 9 * 10^5 = 900,000 possibilities, while for 12-digit palindromic numbers, there are 9 * 10^6 = 9,000,000 possibilities.
90
9
There are 900000 of them.