Final answer:
A DEA number is required by the provider writing the prescription, which allows them to prescribe controlled substances.
Step-by-step explanation:
The provider writing the prescription is required to have a DEA number. A DEA (Drug Enforcement Administration) number is an identifier assigned to a healthcare provider by the DEA that allows them to write prescriptions for controlled substances. This number is not required for the person receiving the prescription, all providers working in a physician's office, or all providers working in a pharmacy, unless these individuals are also prescribing controlled substances. Only those with the legal authority to prescribe such medications need to have this unique identifier.