There is 90 four digit palindromes.
There are no four-digit perfect squares that are palindromes.
There are 90 four-digit palindromes
90
There are four of them
2240
Four
64
9,000
5*5*4*4 = 400
There are 9 x 10 x 10 x 10, or 9000 four-digit number that can be formed if the leading digit cannot be zero.
67 of them.