French Guiana is country code +594. Landline numbers begin with +594 594; mobile numbers begin with +594 694. In either case, there are 6 further digits for the complete telephone number.
Guyana is country code +592.
Suriname (Dutch Guyana) is country code +597.
(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.)
French Polynesia (including the island of Tahiti) is country code +689.
The French special collectivity of New Caledonia is country code +687.
The French overseas territory of Wallis and Futuna uses country code +681.
ISO country code MF is the French northern half of the Caribbean island of Saint-Martin. French Saint-Martin shares telephone country code +590 with Guadeloupe and several other French Caribbean islands. ISO country code SX is the Dutch southern half, Sint Maarten, which is now in North American telephone area code +1 721.
It is not clear what you mean by "national phone code." The telephone country code for France is +33.
Leichtenstein is telephone country code +423.
where is telephone country code 1816
That is not a country code.
A French telephone number beginning with 02 is in the northwest part of the country.
Fiji has telephone country code +679.
Country code +57 is Colombia.
Gibraltar is country code +350.