Telephone numbers are typically composed of an international call prefix, a country calling code and the local telephone number. To aid legibility, they are split into groups, using spaces and not dashes or points. In the Catalan-speaking territories, the numbers after the country calling code are grouped in threes.
Note that the international call prefix (00) used to dial out of a country is generally replaced with a plus sign. This is joined to the country calling code, which is used to dial into a country.
Telephone extensions are written at the end of the number, after a space, in brackets.