Operating Company Number OCN
NANP · also called company code
A four-character code identifying the service provider a numbering resource is assigned to.
An Operating Company Number (OCN) is a four-character alphanumeric code that identifies a telecommunications service provider in numbering and billing records. Each central-office code and thousands-block assignment carries the OCN of its assignee.
A single company often holds many OCNs — commonly one or more per state or per operating entity — so the same carrier can appear under dozens of OCNs across the country. Resolving OCNs back to a real-world company is a distinct data problem.
One company is not one OCN. Large carriers hold many OCNs (often split by state or legal entity), so counting OCNs is not the same as counting companies.