The same as the number of two-digit numbers, since the last two digits
must the same as the first two, only reversed.
So I'll say there are 100 four-digit palindromes.
There are 90 palindromic numbers between 100 and 1000
90
9
There are 900000 of them.
10
There are 90 palindromic numbers between 100 and 1000
infinite
90
9
There are 900000 of them.
There are not just 13 non-palindromic numbers. Most numbers are non-palindromic.
10
1089
1089
Twenty.
1089 palindromes
25001