UK numbers beginning with 074 through 079 are mobiles. From outside the UK, replace the leading '0' with the country code +44, as in +44 7759.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
+44 77 (or 077 in domestic format) is the start of a UK mobile phone number.
However, a number beginning with 07700 or 07797 (or +44 7700 / +44 7797) is a mobile from Jersey (Channel Islands), and a number beginning with 07781 (or +44 7781) is a mobile from the Isle of Man. Although the Isle of Man, Jersey, and Guernsey are technically not part of the UK, they are British crown dependencies and share the telephone country code +44.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
There are various countries that might have 077 as an area code for domestic calls, or that have area codes beginning with 077. You need to be more specific.
where is area code 077
There is no such geographic area code in the UK. All UK geographic area codes start with 01 or 02. Numbers beginning 074, 075, 07624, 077, 078 and 079 are for mobile phones.
All UK area codes begin with a 0. There is no area code 6010 in the UK, and there is no 06010 code either.
UK area code 020 is London.
The country code and area code of Ilocos Sur, Philippines is 63, (0)77.
There is no area code 20 in the UK
There is no 01134 code in the UK.
The country code and area code of Aberdeen, United Kingdom is 44, (0)1224.
Cambridge is in area code 01223, or +44 1223 from outside the UK.
In the UK, 0121 is the area code for Birmingham.
Until the early 1990's, area code +44 21 (or 021 within the UK) was Birmingham, which is now area code +44 121 (or 0121 within the UK). There has never been an area code +44 217 (or 0217) in the UK.