Python, pasted on Dec 22:
 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 ``` ```#Project Euler Problem 3: #What is the largest prime factor of the number 600851475143 ? import time start = time.time() from math import sqrt n = 600851475143 m = n bigO = 0 prime_factors = [] print "n=", n print "--------" #Check if 2 is a factor: while m%2 == 0: print "i = 2, m = ", m print "Factor: 2" prime_factors.append(2) m = m/2 bigO += 1 #Continue with the rest of the odd naturals less than m (which is n with all powers of 2 removed to begin with): i = 3 while i <= m: #print "i = " + str(i) +", m = " + str(m) if m%i == 0: #print "Factor: " , i prime_factors.append(i) m = m/i i -= 2 i += 2 bigO += 1 #if n%m == 0: # print "m=", m print "Prime decomposition: ", prime_factors print "Iterations: ", bigO print "Total elapsed time: " + str((time.time()-start)*1000) + " milliseconds." ```

Output:
 ```1 2 3 4 5 ``` ```n= 600851475143 -------- Prime decomposition: [71, 839, 1471, 6857] Iterations: 3431 Total elapsed time: 9.62114334106 milliseconds. ```