Prime numbers which sum of digits is also prime

Prime numbers which sum of digits is also prime is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Task

Prime numbers n which sum of digits is also prime, where n < 500

Ring

<lang ring> load "stdlib.ring" see "working..." + nl see "Prime numbers which sum of digits is also prime:" + nl

row = 0 limit = 500

for n = 1 to limit

   flag = 0
   sum = 0
   strn = string(n)
   if isprime(n)
      for m = 1 to len(strn)
          sum = sum + strn[m]
      next
      if isprime(sum)
         flag = 1
      ok
   ok
   if flag = 1    
      see "" + n + " "
      row = row + 1
      if row%5 = 0
         see nl
      ok
   ok

next

see nl + "Found " + row + " numbers" + nl see "done..." + nl </lang>

Output:

working...
Prime numbers which sum of digits is also prime:
2 3 5 7 11 
23 29 41 43 47 
61 67 83 89 101 
113 131 137 139 151 
157 173 179 191 193 
197 199 223 227 229 
241 263 269 281 283 
311 313 317 331 337 
353 359 373 379 397 
401 409 421 443 449 
461 463 467 487 
Found 54 numbers
done...