Telephone country codes never begin with zero.
Country code +31, dialed as 00 31 from many places, is the Netherlands, and a number beginning with +31 6 is a mobile phone.
Country code +1, dialed as 003 1 from many places, is North America (USA, Canada, etc.), but you need the three-digit area code (i.e., two more digits) to narrow down the location.
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., +31 or +1), omitting any dialing prefix.
(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.)
The telephone country code 00316 is used for mobile phones in the Netherlands. In this format, "0031" is the country code for the Netherlands, and "6" indicates a mobile phone number. When dialing from abroad, you would use +31 6 followed by the local mobile number.
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.