Nice primes
If n and sumn are prime then n is Nice prime
Let 500 < n < 1000
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You are encouraged to solve this task according to the task description, using any language you may know.
- Take an integer n, greater than zero.
- sumn is sum of n's digits
- If sumn's lenght greater than 1 repeat the (2) for n = sumn
- Stop when sumn's length equal to 1
- Example
853 (prime) 8 + 5 + 3 = 16 1 + 6 = 7 (prime)
Ring
<lang ring> load "stdlib.ring"
num = 0 limit1 = 500 limit2 = 1000
see "working..." + nl see "Nice numbers are:" + nl
for n = limit1 to limit2
strn = string(n) while true sumn = 0 for m = 1 to len(strn) sumn = sumn + number(strn[m]) next if len(string(sumn)) = 1 exit ok strn = string(sumn) end if isprime(n) and isprime(sumn) num = num + 1 see "" + num + ": " + n + " sumn = " + sumn + nl ok
next
see "done..." + nl </lang>
- Output:
working... Nice numbers are: 1: 509 sumn = 5 2: 547 sumn = 7 3: 563 sumn = 5 4: 569 sumn = 2 5: 587 sumn = 2 6: 599 sumn = 5 7: 601 sumn = 7 8: 617 sumn = 5 9: 619 sumn = 7 10: 641 sumn = 2 11: 653 sumn = 5 12: 659 sumn = 2 13: 673 sumn = 7 14: 677 sumn = 2 15: 691 sumn = 7 16: 709 sumn = 7 17: 727 sumn = 7 18: 743 sumn = 5 19: 761 sumn = 5 20: 797 sumn = 5 21: 821 sumn = 2 22: 839 sumn = 2 23: 853 sumn = 7 24: 857 sumn = 2 25: 887 sumn = 5 26: 907 sumn = 7 27: 911 sumn = 2 28: 929 sumn = 2 29: 941 sumn = 5 30: 947 sumn = 2 31: 977 sumn = 5 32: 983 sumn = 2 33: 997 sumn = 7 done...