Estonia uses country code +372(dialed as 00 372 from many places).
(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 code +37 is not assigned to any single country but was historically used for several countries in the former Soviet Union. After the dissolution of the USSR, the code was split, and specific codes were allocated to individual countries. Notably, +370 is assigned to Lithuania, while +371 is for Latvia, and +372 is for Estonia.
Country code +372 is Estonia, and +372 81 is a mobile.
Leichtenstein is telephone country code +423.
where is telephone country code 1816
The country code and area code of Amacueca, Mexico is 52, (01)372.
The country code and area code of Ljungby, Sweden is 46, (0)372.
The country code and area code of Dushanbe, Tajikistan is 992, (8)372.
The country code and area code of Zonguldak, Turkey is 90, (0)372.
That is not a country code.
Country code +57 is Colombia.
Country code 52 is Mexico.
Fiji has telephone country code +679.