486 162 54 18 6 _____

2

To find the missing number in the sequence, we can divide each number by 3.

486 ÷ 3 = 162
162 ÷ 3 = 54
54 ÷ 3 = 18
18 ÷ 3 = 6
6 ÷ 3 = 2

Therefore, the missing number is 2.