(10 billion) possible combinations
Posted: Thu May 22, 2025 6:56 am
Format: NANP numbers are 10 digits: (Area Code) XXX-XXXX.
Area Code (NPA): 3 digits.
Central Office Code (NXX): 3 digits.
Subscriber Number (XXXX): 4 digits.
Theoretical Maximum (NANP): With 10 digits, there are 10
10
Actual Usable Numbers (NANP): This theoretical albania phone number list maximum is significantly reduced by rules:
NPA (Area Code) Rules: The first digit of an area code cannot be 0 or 1. The second and third digits have some restrictions as well (e.g., N11 codes are reserved). This limits the number of valid area codes.
NXX (Central Office Code) Rules: The first digit cannot be 0 or 1. Certain NXX combinations are reserved (e.g., 555 for fictional numbers, though only 555-0100 to 555-0199 are strictly reserved for fiction, the rest are for information services; 958/959 for testing).
Special Codes: Many 3-digit N11 codes (like 911 for emergencies, 411 for directory assistance, 811 for "call before you dig") reduce the available numbers.
Allocation Blocks: Numbers are typically allocated to carriers in blocks (e.g., thousands-blocks), and even if only a few numbers in a block are used, the entire block is considered allocated. This leads to "number churn" and inefficiency.
Estimated Capacity (NANP): Despite the 10
10
theoretical possibilities, the actual number of usable 10-digit NANP numbers is estimated to be around 6.4 billion. This number is further constrained by the number of available area codes and the efficiency of their allocation.
Area Code (NPA): 3 digits.
Central Office Code (NXX): 3 digits.
Subscriber Number (XXXX): 4 digits.
Theoretical Maximum (NANP): With 10 digits, there are 10
10
Actual Usable Numbers (NANP): This theoretical albania phone number list maximum is significantly reduced by rules:
NPA (Area Code) Rules: The first digit of an area code cannot be 0 or 1. The second and third digits have some restrictions as well (e.g., N11 codes are reserved). This limits the number of valid area codes.
NXX (Central Office Code) Rules: The first digit cannot be 0 or 1. Certain NXX combinations are reserved (e.g., 555 for fictional numbers, though only 555-0100 to 555-0199 are strictly reserved for fiction, the rest are for information services; 958/959 for testing).
Special Codes: Many 3-digit N11 codes (like 911 for emergencies, 411 for directory assistance, 811 for "call before you dig") reduce the available numbers.
Allocation Blocks: Numbers are typically allocated to carriers in blocks (e.g., thousands-blocks), and even if only a few numbers in a block are used, the entire block is considered allocated. This leads to "number churn" and inefficiency.
Estimated Capacity (NANP): Despite the 10
10
theoretical possibilities, the actual number of usable 10-digit NANP numbers is estimated to be around 6.4 billion. This number is further constrained by the number of available area codes and the efficiency of their allocation.