To answer this question we will construct the factor tree.
Computing the subtraction we get:

Dividing the above result by 5 we get:

Dividing by 7 we get:

Dividing by 19 we get:

Dividing by 577 we get:

Notice that 1009 is a prime number.
Therefore the factor tree is as follows:
Answer: The prime factors of (3^18 - 2^18) are 5, 7, 19, 577, and 1009.