The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?
The answer is 6857, as surmised by the following program.
#include <iostream> #include <math.h> int main(void) { unsigned long long factoredNumber = 600851475143; unsigned long long seed = 2; // Could limit the search the search to less than square root of factoredNumber, due to it being composite while(pow(seed, 2) <= factoredNumber) { // While the "seed" is now a factor of factoredNumber while(factoredNumber%seed == 0) { // Divide and replace factoredNumber = factoredNumber / seed; } // Iterate seed += 1; } std::cout << factoredNumber; return 0; }