How many numbers in a palindrome?

Answer 1

One.

If you mean "digits", the number can have any amount of digits; the only requirement to be called a "palindrome" is that if you read it backwards, you get the same sequence of digits. Thus, any of the following is a palindrome: 1 (any 1-digit number is a palindrome), 55, 121, 2002, 12321, 600006, 8105018, ... As you can see, you can make them arbitrarily large.