I typed GCF(34,784) into my calculator, and got \(\boxed 2\) as my GCF.
I did the same for the LCM and got \(\boxed{13328}\).
http://www.mathematicsmagazine.com/applications/GCF_LCM.htm
You can use this to find both of them if you do not have a calculator that can calculate GCF and LCM.
The Greatest Common Factor
The greatest common factor, or GCF, is the greatest factor that divides two numbers. To find the GCF of two numbers:
List the prime factors of each number.
Multiply those factors both numbers have in common. If there are no common prime factors, the GCF is 1.
The Least Common Multiple
A common multiple is a number that is a multiple of two or more numbers. The common multiples of 3 and 4 are 0, 12, 24, ....
The least common multiple (LCM) of two numbers is the smallest number (not zero) that is a multiple of both.
What is the GCF and LCM of 34 and 784?
\(\begin{array}{|rcll|} \hline 34 &=& 2^1\cdot 17^1 \cdot (7^0) \\ 784 &=& 2^4\cdot 7^2 \cdot (17^0) \\\\ && \begin{array}{|rcll|} \hline \text{gcf}(34,784) &=& 2^1\cdot 17^0 \cdot 7^0 \quad & | \quad \text{min exponent} \\ &=& 2\cdot 1 \cdot 1 \\ &=& \mathbf{2} \\\\ \text{lcm}(34,784) &=& 2^4\cdot 17^1 \cdot 7^2 \quad & | \quad \text{max exponent} \\ &=& 16\cdot 17 \cdot 49 \\ &=& \mathbf{13328} \\ \hline \end{array}\\ \hline \end{array}\)