Limit Us Phone Title For Free

Yet with the rollout of three additional digits at the front of every phone number, suddenly the total number of possible combinations jumped from 10 million to a whopping 10 billion.

The standard requires that a telephone number has a maximum of 15 digits, separated as the first one to three digits as a country code and the remaining digits corresponding to the subscriber's telephone number.

But area codes, too, are finite. There are 800 possible three-digit combinations (using 0 or 1 as the first digit of an area code is invalid), but many are unusable (think 911) or reserved for official use. Ultimately, the math works out to a bit more than 5 billion total available phone numbers.

US phone numbers are laid out as area code (3 digit), prefix (3 digit), suffix (4 digit) for a total of 10 digits not including country code (+1). While it may seem we have plenty of phone numbers to go around, we really don't. Each suffix can only accommodate for 10,000 assignable numbers (0000 through 9999).

That dates back to the late 1940s when AT&T developed the North American Numbering Plan (NANP) to simplify dialing calls, mostly long-distance. The plan went into effect in 1951. NANP numbers include 10 digits: a three-digit area code and a seven-digit local number. The format is usually represented as NXX-NXX-X.

Therefore, we have 544320 ways of seven-digit phone numbers can be formed if the first digit cannot be 0 and repetition of digits is not permitted.

10 x 10 = 100. In the same fashion, if phone numbers were to have 9 digits, this would only satisfy 1,000 million (100 crore) subscribers. Hence, the 10-digit mobile number. This offers us 10 billion (1000 crore) different combinations, and as for the global population, it is highly unlikely to exceed this capacity.