Prime Palindromes

I haven’t done a math puzzle in a while. Maybe a year? But I play with math. A lot. If I see puzzles, why not share them?

What is the largest 4-digit prime palindrome?

Prime – a number whose only factors are 1 and itself. “Number” here clearly means Natural Number, or in many text books Counting Number, a number from the set {1, 2, 3, …}, a positive integer… Except we exclude 1 itself. The smallest prime is 2. The rest of the primes are odd. And we know there is not a biggest prime. Hmmph. I should write up some prime basics. But not here.

Palindrome – a word that reads the same backwards and forwards. Like KAYAK. Or a phrase that reads the same forwards and backwards. Like “A man, a plan, a canal, Panama.” Or a number that reads the same forwards and backwards. Like 99. Or 121. Does 7 count? Good question.

Largest? That’s easy.

4-digit? Any number with four digits. 1000 is the smallest. 9999 is the largest. There are nine thousand of them (if this surprises you, see if you can convince yourself that it is correct.

And that’s it:

What is the largest 4-digit prime palindrome?