They are composed of a combination of an area code and a local line or subscriber telephone number.
Local telephone numbers contain from five to seven digits, and may vary within the area code.
Mobile phone numbers start with 070, 080 or 081, 090 or 091 and are followed by eight digits.
[1] Nigeria implemented mobile number portability in 2013.
Therefore, prefixes no longer reliably indicate the parent network of a number.