What format is primarily used to represent E.164 numbers in DNS records?

The correct and primary format used to represent E.164 numbers in DNS records is string format. E.164 is an international telephone numbering plan that provides a unique identifier for each participant in the global telephone network. When these numbers are represented in DNS records, they are typically formatted as strings, which allows for easy readability and consistency across different systems.

Using string format helps ensure that the numbers are universally understood and can be processed by various software and services without confusion. For instance, a representation like "+14155552671" is straightforward and aligns with the common international dialing format.

Other formats, such as binary, decimal, or hexadecimal, could create complications with readability and consistency when managing phone numbers within DNS records, which is why string format is the standard choice. This choice simplifies integration and usage across different telecommunications systems and protocols.