I was wondering if anyone has a particular method of working out the prime factoring of say numbers greater than 3 digits.
Thanks
BIOS
Example
Now, check to see if all primes divide 627.
If 0,2,4,6,8| the last digit, then 2|627
If , then 3|627.
For 5, the last digit needs to be 0 or 5.
For 7, double the last digit 7*2=14 and subtract it from the remaining digits 62-14=48, and if 7|48, then 7|627.
For 11, subtract the last digit from the remaining digits 62-7=55, and if 11|55 which it does, then 11|627.
For 13, add 4 times the last digit 62+28=90, and if 13|90, then 13|627.
I only know rules for up to 13.
Thanks for the replies.
Dwsmith that's what i suspected. Just learn the divisibility rules for all primes up to say 13 is probably the most practical way. Was just wondering if there was an alternate method i should be aware of :P
Hey no just mean by pen and paper or mentally
Thanks for the clarification! I thought as much. So to sum up the best way is to just start at the smallest prime and move upwards if they don't pass the divisibility rule. I don't know if it's just me but i always feel like i'm cheating when i use those tricks/rules!
There are so many resources available. Doing thing by hand is a waste of time.
Look at this site.