Which number is used by service providers to verify the validity of a call over their networks?

The number used by service providers to verify the validity of a call over their networks is the Electronic Serial Number (ESN). The ESN is a unique identifier assigned to mobile devices that operate on CDMA (Code Division Multiple Access) networks. It plays a crucial role in distinguishing one mobile device from another on the network, allowing service providers to manage connections, authentication, and billing effectively.

When a device attempts to make or receive calls, the service provider's network checks the ESN against its database to ensure the phone is authorized and active. This helps prevent fraudulent use of the network and ensures that the service is provided only to legitimate subscribers.

Other identifiers, such as the International Mobile Equipment Identity (IMEI), Mobile Equipment Identifier (MEID), and Integrated Circuit Card Identifier (ICCID), serve different purposes in mobile communication. The IMEI is primarily used for identifying GSM and UMTS devices, the MEID is often used for identifying devices on CDMA networks similar to ESN but serves newer standards, and the ICCID is related to the SIM card itself, identifying the card's subscription on GSM networks. However, for the specific task of verifying the validity of a call over networks that utilize the ESN, this number is paramount