Find the smallest prime that remains prime
when added to its reversal
P&P solution preferred
Assuming I didn't miss a smaller one: 239 is prime and 239+932=1171 which is also prime.
The number cannot be one digit because the sum would be even.
The number cannot be two digits because the sum would be divisible by 11.
If the number is three digits the first cannot be 1 the last would have to be even for the sum to be odd.
If the number is three digits the middle digit cannot be 0 or the sum will be divisible by 101.
From here I searched by hand ignoring obvious multiples of 3 and 5: 211, 217, 219, 221, 223, 227, 229, 233, 237, 239
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Posted by Jer
on 2018-09-24 11:42:11 |
Possible solution
