Currently the Excel default formatting is:
1,000,000 500,000 How do you format the number to use the comma separator (,) like this
10,00,00,000 50,00,000 This is is how Indian Currency (Rupees, INR, ₹) is normally represented.
32 Answers
Some currency systems require a slightly different comma schema. With data like:

applying this Custom Number Format with decimal points:
[>=10000000]##\,##\,##\,##0;[>=100000] ##\,##\,##0;##,##0.00 will produce:

There is a better and permanent solution (for Indian users):
Add Region as India and language as English(India). Then you can see the Indian comma format and Indian currency symbol inplace of dollar symbol. Default setting in US and English(US).
Go to Control panel > Region (search)
(tab) Format : Select English(India)
Click Laguage Preferences and add English(India) and move up to top.
Press OK