There is no specific number for one international operator, rather each country differs in calling codes and procedures. For example, to reach an international operator in the United Kingdom, one would press 155, but this would only be valid for calls within the U.K.
The access number to place international calls remains the same for every country, and that number is 011. To place an international call, one would need that code as well as the country's code. For example, Argentina's country code is 54. For help in dialing international calls from within the United States, one can press the operator code for the U.S., which is 0.