The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?

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          #define N 600851475143bool prim(int n){ int i; for(i=2; i*i<=n; i++) { if(n%i==0) return false; } return true;}int main(){ long long s=sqrt(N); while(s--) { if(s%2!=0 && prim(s) && (N%s==0)) { printf("%lld\n",s); break; } } return 0;}
         
        
       
      
     
    

Answer:

6857