How to write a valid mobile phone number in international format?

A valid phone number in international format is as the following example

[country code] [network prefix] [number]

44 831 1234567

Other examples:

USA: 12481234567 (Country Code = 1, network prefix = 248, number = 1234567)

France: 3311234567 (Country Code = 33, network prefix = 1, number = 1234567)

UK: 440848 9123 456 (Country = 44, network prefix = 848, number = 123456)

SA: 27821234567 (Country Code = 27, network prefix = 82, number = 1234567)

Pak: 923001234567 (Country Code = 92, network prefix = 300, number = 1234567)

South Korea: 821012345678 (Country Code = 82, network prefix = 10, number = 12345678