California Code, Public Utilities Code - PUC § 7935

(a) The commission shall develop and implement any measures it determines to be available for telephone corporations that possess prefixes to efficiently allocate telephone numbers within those prefixes. The commission shall consider the cost effectiveness of these measures before requiring implementation. Among the measures the commission shall consider are rate center consolidation, allocation of numbers in blocks smaller than 10,000, and unassigned number porting.

(b) For the purpose of this section, in accordance with the North American Numbering Plan, a telephone number consists of a three digit area code or number plan area (NPA), a three digit prefix or NXX code, and a four digit line number.