The plain hash itself does not give any indication of the number of iterations. But with practical schemes, such as most
crypt based ones, the number of iterations is stored alongside hash and salt in the database.
Keeping the number of iterations secret doesn't gain you much security in practice. Figuring out the number of iterations isn't that hard in practice. Choose a few users who probably have weak passwords, and compare after each iteration. Or if you can register your own accounts, you can simply attack that single user whose password you know.
If you want to improve security in a scenario where the attacker obtains only the database, but not the source-code/config file, there are much better techniques than a secret number of iteration. For example you could concatenate the salt with a secret key, or encrypt the hash. That way an attacker has no chance of attacking the hashes without gaining access to the place where you store the key.