197

Just showing those entries submitted by 'Gallardo': (Click here to show all)

+ 197 is the sum of digits of all two-digit primes. [Gallardo]

+ The smallest multidigit prime p that makes 10^p-9 prime. Note that the next prime (199) has the same property. They are twin primes! [Gallardo]

Printed from the PrimePages <primes.utm.edu> © G. L. Honaker and Chris K. Caldwell