STD Code

Subscriber Trunk Dialling (STD) codes are assigned to each city/town/village, with the larger Metro cities having shorter area codes (STD codes), the shortest being 2 digits. Land line numbers are at most 8 digits long (usually in major metros). The total length of all phone numbers (STD code and the phone number) in India is constant at 10 digits.

No prefix is required to call from one landline to another in the same STD area. A prefix of "0+STD code" is required to dial from a landline phone in one STD code area to another. A prefix of "0+STD code" is required to dial from a mobile phone in India to any landline number, irrespective of STD area.

Telemarketing 

Telemarketers have been issued 10-digit telephone numbers starting with 140 (140XXXXXXX) by the Department of Telecommunications on TRAI's request.