List of country calling codeswikipedia
Country calling codes or country dial in codes are telephone dialing prefixes for the member countries or regions of the International Telecommunication Union (ITU).
Country CodeDialing codeTelephone codecountry calling codeCalling codecode for international direct dialinternational dialing codeinternational calling codeinternational dialling code+91

North American Numbering Plan

Area codeArea codes<span style="white-space:nowrap;">Area code(s)
For example, the international call prefix in all countries belonging to the North American Numbering Plan is 011, while it is 00 in most European, Asian and African countries.
For international call routing, the NANP has been assigned the international calling code 1 by the International Telecommunications Union (ITU).

Telephone numbering plan

Area codeCalling codearea codes
Country codes are a component of the international telephone numbering plan, and are necessary only when dialing a telephone number to establish a call to another country.
The standard defines a country calling code (country code) for each state or region which is prefixed to each national numbering plan telephone number for international destination routing.

List of international call prefixes

International call prefixinternational access code+
By convention, international telephone numbers are represented by prefixing the country code with a plus sign, which also indicates to the subscriber that the local international call prefix must first be dialed.
The international dialing prefix must be dialed before the country calling code and the destination telephone number.

Telephone numbers in South Africa

+27031Area code
When dialed from another country, the '0' is omitted and replaced with the appropriate international access code and the country code 27.

E.164

e164.arpae164.orge.164
They are defined by the ITU-T in standards E.123 and E.164.
The presentation of a number is usually prefixed with the plus sign, indicating that the number includes the country calling code.

Telephone numbers in Serbia

Area code+381(0)13+381(0)23
The country calling code of Serbia is +381.

Telephone numbers in Montenegro

Area code+382Montenegro
Until Montenegro gained independence from Serbia and Montenegro, the nation was accessed through the international dialing code +381.

Telephone numbers in Paraguay

+595
Telephone numbers in Paraguay all have the same format since 2002, consisting of the country code (595), followed by a phone number.

Telephone numbers in Cuba

+53
Telephone numbers in Cuba all have the same format, consisting of the country code (53), followed by an area code.