Write a function to determine if a number is divisible by 16. This can be done by a few different methods. Here are two:

1. If a number has four or more digits, take the last three digits. Add eight to it if the thousands digit in the original number is odd (zero if even). If this three-digit number is divisible by 16, so is the original number. The resulting number can also be reduced by the following method.
2. Take the last two digits and add them to four times the remaining number. Apply this method recursively until a two-digit number remains. As usual, if the resulting number is divisible by 16, then so is the original number.

A few of the function restrictions have been lifted.

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