Yeah, all numbers in the format of +91-9XXXXXXXXX (10 digits starting with 9) are mobile numbers, but not all mobile numbers start with 9. They even start from 7 or 8 also now.
Landline numbers, for metro cities are like +91-11-2XXXXXXX
+91=International code,
next 2 digits= city code,
next digit(2)= Telecom provider Identifier
Delhi = 11, Bombay = 22, Madras = 44, Calcutta = 33(Maybe)
Now, In north India, all city codes will start with 1
South India, it will always be 4,
East India = 3 and
West India 2
Tier 2 cities have codes in three digits.. Like Ludhiana = 161, Jalandhar = 181
The Tier3 cities will have code in four digits.. Like 1823 for Nawanshar, 1826 for Phillaur etc..
After city code, 2 is used by BSNL, 5 by Connect..
Here, at this site,
Indiatrace.com - Trace Track Find Mobile number cell number location - You can trace any mobile number. It will tell only the State name and Service Provider in which the number initially was used. For mobile, it is very easy to retain same number and change service provider, known as MNP (Mobile Number Portability), a fairly new concept as compared to west..
The home page,
http://www.indiatrace.com also let one trace land line numbers also..among other things..