Only two countires , l'Egypt and South Africa have a two digit country code.

In Africa the telephone codes indicate the geographic location of each country
the countries of the North have a code like 20 (Egypt), 2I- (Magreb countries),
and the more you go South the more the code increases
Southern Countries have the codes 26-
(Zambia, Madagascar, Zimbabwe ..)
or 27 (South Africa),
28 has never been issued,
(29I for Eritrea is an exeption, the code was issued much later)