Yes. The exchange (middle three for US numbers) also has patterns. More on the allowed codes is here: http://en.wikipedia.org/wiki/North_American_Numbering_P

Yes. The exchange (middle three for US numbers) also has patterns. More on the allowed codes is here: http://en.wikipedia.org/wiki/North_American_Numbering_Plan http://en.wikipedia.org/wiki/North_American_Numbering_Plan although, in practice, many of the allowed codes are not occupied. For instance, no exchange around LA would be 213, and no exchange near SF would be 415.