00 is not an area code in any country.
00, 00x, 00xx, or 00xxx are codes used in many countries as a prefix to an international call. For example, to call from France to Sweden (country code +46), you dial 00 46. To call from Tanzania to Australia (country code +61), you dial 000 61. To call from Nigeria to Tunisia (country code +216), you dial 009 216. To call from Australia to Mexico (country code +52), you dial 0011 52.
(The plus sign means "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.)
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.
Liberia is country code +231.