An easily-recognizable code, in the North American Numbering Plan, is any area code that ends in double digits, such as 800, 877, 900 and 700.

The state of Nevada requested that its new area code be "lucky" 777; this was denied by NANPA because it is an ERC, to be used only for special purposes like inward Wide Area Telephone Service (Northern Nevada was granted 775).

References

• http://www.nanpa.com/pdf/pl-nanp-168.pdf