In the United Kingdom, 020 is the area code for London.
The following four digits of the number, 7138, show that the number was originally issued by Cable & Wireless.
It is not possible to give a more precise location, and a quick web search shows numbers in the range 020 7138 xxxx in use right across London, from the inner city right out to Heathrow and beyond.
London is area code 020. You would need the next two digits to know which part of London. All that can be said from the given digits is that it probably isn't a central London number, although with number portability, even that's not 100% certain.
The 020 area code is London, but a number beginning with 020 7131 is a "virtual" number that could be anywhere in London.
Area code 020 is London, UK.
In the UK, area code 020 is London.
0208387
This isn't a London code. It is the area code for Brentwood in Essex which is about 30 miles northeast of London.
The country code and area code of East London, South Africa is 27, (0)43.
London is area code 020.
In the UK, area code 020 is London. There is no area code 0208.
Bromley is covered by the area code for London, which is 020.
UK area code 020 is London.
In the UK, there is no area code 0207. Area code 020 is London. Number portability means that it is no longer reliably possible to narrow down a London number to a particular neighbourhood by the first few digits of the number. In fact, the "inner/outer" distinction formerly in the digit 7 or 8 following the area code, no longer holds firm.
The area code for London is 020, or +44 20 from outside the UK.
A UK telephone number like (020) 84xx xxxx will be in London. You need to state two more digits in order to be able to work out which part of London; eg. (020) 8484 or (020) 8411 etc.
Area code 020 is London, including the old "inner London" and "outer London" areas.
This is a code for an area of London but has been written incorrectly. It should read 020 3634
In the UK, area code 020 is London. A number beginning with 020 8488 could be located anywhere in the 020 London area. It is not possible to specify the location more specifically.