How many subsets of the set of divisors of $72$ contain only composite numbers? For example, $\{8,9\}$ and $\{4,8,12\}$ are two such sets. Include the empty set in your count.
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
How many subsets of the set of divisors of $72$ contain only composite numbers? For example, $\{8,9\}$ and $\{4,8,12\}$ are two such sets. Include the empty set in your count.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
512
How many subsets of the set of divisors of $72$ contain only composite numbers? For example, $\{8,9\}$ and $\{4,8,12\}$ are two such sets. Include the empty set in your count.
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