Find the missing number of the following series?16 8 24 12 36 18 54 ? 81

The given series is: 16, 8, 24, 12, 36, 18, 54, ?, 81

This series alternates between multiplication and division.

Step 1: Start with 16. Divide it by 2 to get 8. Step 2: Multiply 8 by 3 to get 24. Step 3: Divide 24 by 2 to get 12. Step 4: Multiply 12 by 3 to get 36. Step 5: Divide 36 by 2 to get 18. Step 6: Multiply 18 by 3 to get 54. Step 7: The next step would be to divide 54 by 2, which gives 27.

So, the missing number in the series is 27.