Prior to 1995, all area codes in North America (USA, Canada, etc.) had the first digit 2 through 9, the middle digit 0 or 1, and the last digit 0 through 9, but the second and third digits could not be 00 or 11. That made a total of 8x2x9 = 144 possible geographic area codes.
The 8 N00 codes were reserved for non-geographic special purposes (800 toll-free, 900 premium numbers, 700 special per-carrier numbers, and 500 personal numbers). The 8 N11 codes were reserved to prevent confusion with the special codes like 911 emergency.
Beginning in 1995, the middle digit could be any number from 0 through 8, but area codes with 9 as the middle digit are still reserved for future expansion. There are now 648 possible geographic area codes, give or take a few special cases.
Before area codes, telephone areas in North America were defined by reference to the nearest large city.
The whole point of area codes is that the same prefix can exist in many different area codes, so there is no possible way to answer your question.
In the North American system with 3-digit area codes and 7-digit local numbers, there are slightly less than 8 million possible telephone numbers per area code, so with two area codes you have more than 15 million possible numbers. However, only a fraction of those numbers will be in use at any given time.
There are 900 possible three-digit numbers not beginning with 0. (Note, however, that this question does not accurately describe the restrictions on numbers that can be used as area codes.)
It depends on how many digits in an area code. North America (USA, Canada, etc.) uses a uniform system of 3-digit area codes, but many other countries do not. Assuming a 3-digit area code and no other restrictions other than "first digit not zero," that leaves 900 possible area codes.
In 1995, all UK geographical area codes were converted to begin with 01.
If you look at maps, you will not find area codes. Area codes can be found on area code locator websites. Another place to find area codes is in the telephone directory.
There have been no area codes in England, or the rest of the United Kingdom, that begin with '04' since the year 2000. If the number you have dates from before the major national renumbering in year 1995, it would be the code for Guildford. That code has since changed to 01483.
January 7, 1984 http://en.wikipedia.org/wiki/Area_code_818
With the restrictions specified in your question, there are 8 x 2 x 10 = 160 possible area codes. However, those restrictions do not match the restrictions on actual area codes in North America (USA, Canada, etc.). North American area codes have the first digit not 0 or 1, the second digit not 9, and the third digit not the same as the second digit (such codes are reserved for special purposes like toll-free), leaving 8 x 9 x 9 = 648 possible area codes.
North American area code +1 809 is the Dominican Republic. Although calls to area code 809 are dialed as 1-809-number from the rest of North America (USA, Canada, and some Caribbean/nearby islands), international call charges will apply. Area codes +1 829 and +1 849 also serve the Dominican Republic. For a list of all North American area codes outside the US and Canada, see the related link.
Area codes in the US and Canada were introduced in 1947.