To solve this expression, we need to follow the order of operations (PEMDAS/BODMAS).

First, let's simplify the expression inside the parentheses:
21 - 18 = 3

Now, let's simplify the expression inside the square brackets:
19 - 2(3) = 19 - 6 = 13

Finally, let's solve the expression outside the square brackets:
2345 - 1000 ÷ 13

To divide 1000 by 13, we get:
1000 ÷ 13 = 76.92307692307692

Now, subtracting this value from 2345:
2345 - 76.92307692307692 = 2268.076923076923

Therefore, the final answer is 2268.076923076923.