challenge - prime numbers where sum of squared digits of prime number is also prime

[Gilles59]

User RPL with ListExt Library (https://www.hpcalc.org/details/7971) :

Code:

 {} 1
 WHILE DUP 1000 < REPEAT
  NEXTPRIME DUP I->NL SQ LSUM ISPRIME? {SWAP OVER + SWAP} IFT
 END
 DROP

same results as Didier

"What is the largest prime less than 100,000 where this is true?"

Code:

 100000
 DO 
  PREVPRIME 
 UNTIL DUP I->NL SQ LSUM ISPRIME? END

-> 99971

For 1'000'000'000 -> 999'999'667