The GCD of given numbers is 569.
Step 1 : Find prime factorization of each number.
$$\begin{aligned}1219936 =& 2\cdot2\cdot2\cdot2\cdot2\cdot67\cdot569\\[8pt]642401 =& 569\cdot1129\\[8pt]\end{aligned}$$(view steps on how to factor 1219936 and 642401. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}1219936 =& 2\cdot2\cdot2\cdot2\cdot2\cdot67\cdot\color{blue}{\boxed{569}}\\[8pt]642401 =& \color{blue}{\boxed{569}}\cdot1129\\[8pt]\end{aligned}$$Step 3 : Multiply the boxed numbers together:
$$ GCD = 569 $$This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.