Telephone country codes never begin with zero.
Country code +211, dialed as 00 211 from many places, was assigned in 2011 for the new nation of South Sudan.
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., +211 or +64), 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 is00, but North America (USA, Canada, etc.) uses 011, Japan uses010, Australia uses0011, and many other countries use different prefixes.)
0021 is not the country code for England. England uses the United Kingdom country code +44 which is dialled as 00 44 from most of Europe or 011 44 from North America.
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.