Telephone country codes never begin with zero.
Country code +999, dialed as 00 999 from many places, is unused. It is reserved for an unspecified future global service.
Country code +99, dialed as 009 99 from many places, is an incomplete code for a former Soviet republic in Central Asia, or for ITPCS, or for the aforementioned future global telecommunications service.
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., +992 or +377), 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.)
Leichtenstein is telephone country code +423.
where is telephone country code 1816
That is not a country code.
Country code +57 is Colombia.
Country code 52 is Mexico.
Fiji has telephone country code +679.
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.