You got me to wondering about area code 666. The internet, as almost always, supplies the information. There seems to be no 666 in the US (I can't imagine why). The numerically nearest country code is 664, which is Montserrat (a volcanic island in the Leeward Islands of the British West Indies, southeast of Puerto Rico, northwest of Guadeloupe in the Caribbean). Saudi Arabia is 966, which is intriguingly close.
I've also learned that the country code for Ecuador is 593, and the Galapagos Islands have an area code of 05. All their phone numbers have six digits preceded by an area code. So to make an international call to the Galapagos Islands you'd dial 011-593-05 + six digits. (Darwin Central, being sovereign, doesn't use Ecuador's numbers; we have our own code -- which you know so well.)
And one more piece of fascinating information: The zip code for Topeka, Kansas is 66601. 66606 is also in Topeka. Make of that what you will.
Is there any area code which is a triple repeated digit?
Until a few years ago, all area codes in the US had a "0" or a "1" as their middle digit. That's what allowed the phone system to "know" whether you were trying to call a local exchange via long distance, or were trying to call into another area code. But because we were running out of phone numbers under that numbering system, they had upgrade the the phone system to handle area codes with middle digits OTHER than zero and one.
I'll bet if you do a Google search, you'll find something that decribes the whole thing in much more detail than I could possible provide, or care about....
;-)