Telephone country codes never begin with zero.
Country code +24, dialed as 00 24 from many places, is an incomplete code in Africa. You need one more digit to specify the country.
Country code +4, dialed as 002 4 from many places, is an incomplete code in Europe. You need one or two more digits to specify the country.
To avoid confusion, it is best to write an international telephone number in correct international format, beginning with the plus symbol and the correct telephone country code (e.g., +241 or +44), omitting any dialing prefix.
(The plus signmeans "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
0024 - is incomplete. The next digit after the 4 is needed to specify the country it belongs to. There are TEN countries with IDC beginning 0024 !
Leichtenstein is telephone country code +423.
where is telephone country code 1816
That is not a country code.
Fiji has telephone country code +679.
Country code +57 is Colombia.
Gibraltar is country code +350.
Moldova is country code +373.
Slovenia is country code +386.
Vanuatu is country code +678.
Niue is country code +683.
Togo is country code +228.