If it's an area code, it's incomplete. In which case, "001" would be the international dialing prefix to call the US from a foreign country, and "65" would only be the first two digits of a three digit area code. We'd need the last digit to tell you.
If you meant ZIP code, there is no such ZIP code in use in the US.
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.
Togo is country code +228.