The GCD of given numbers is 1.
Step 1 : Find prime factorization of each number.
$$\begin{aligned}18021945 =& 3\cdot5\cdot43\cdot27941\\[8pt]3440835 =& 3\cdot3\cdot5\cdot76463\\[8pt]1003650 =& 2\cdot3\cdot5\cdot5\cdot6691\\[8pt]2443387 =& 2443387\\[8pt]\end{aligned}$$(view steps on how to factor 18021945, 3440835, 1003650 and 2443387. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}18021945 =& 3\cdot5\cdot43\cdot27941\\[8pt]3440835 =& 3\cdot3\cdot5\cdot76463\\[8pt]1003650 =& 2\cdot3\cdot5\cdot5\cdot6691\\[8pt]2443387 =& 2443387\\[8pt]\end{aligned}$$Note that in this example numbers do not have any common factors.
Step 3 : Multiply the boxed numbers together:
Since there is no boxed numbers we conclude that $~\color{blue}{ \text{GCD = 1} } $.