Look at any book published outside India you find comma for numbers after every three digits. but we put comma first after three digits and then after every two digits.
we call this twelve crore, thirtyfour lakh, fifty six thousand seven hundred and eighty nine. That is not intelligible to the westerners. They use commas as follows and call it:
one hundred and twenty three million four hundred and fifty six thousand seven hundred and eighty nine.
the correct order from right to left is:
units, tens, hundreds, thousands, ten thousands, hundred thousands, millions, ten million hundred millions, then billion etc…