Sometimes we forget our mobile number and face a lots of difficulties to give our number to someone. So you don't have to face difficulties for this because i have some USSD code to know our mobile numbers.
Here are the list of some USSD code. Only you have to dial that code,
Vodafone = *111*2#
Aircel = *122*131#
Airtel = *121*9#
Reliance, Smart, BSNL, Tata Docomo, = *1#
Mtnl = *8888#
Idea = *131*1# OR *131#