Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Is there any proof of infinitude of http://oeis.org/A007500 primes.

If you want to generate them here is trivial and naive python program.

def is_prime(n):
    i = 2
    while i*i <= n:
        if n%i == 0:
            return False
        i = i + 1
        return True

print [x for x in range(1,200) if is_prime(x) and is_prime(int(str(x)[::-1]))] 
share|improve this question
This is called a palindromic prime. See the wikipedia page, the Wolfram page, and Prime Glossary page. (Unfortunately, not much seems to be known about this question.) –  Srivatsan Oct 17 '11 at 19:59
Specifically, that link says "It is not known if there are infinitely many palindromic primes in base 10." But, that doesn't mean someone can't figure out a proof! –  Graphth Oct 17 '11 at 20:10
I would guess that the $n^{th}$ palindromic prime might be of the order of $n (\log_e n)^2$ in any base (with some fluctuation around this since all bar the first and third can only start with 1, 3, 7 or 9). –  Henry Oct 17 '11 at 21:08
@Henry: The $n(\log n)^2$ is very reasonable. The constant might need adjustment, because if $n$ is not divisible by $3$ or $11$, neither is its reversal. –  André Nicolas Oct 17 '11 at 21:43
Paul Erdős said, allegedly, about the Collatz conjecture: "Mathematics is not yet ripe for such problems". I asked this question because I suspected this one to be one of "such problems". –  Pratik Deoghare Oct 18 '11 at 2:13

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.