Is my spelling right - a hundred seventy two billion one hundred forty seven million a hundred and twenty two point a quarter? Thank you.
Since the British officially agreed that a billion was a thousand million rather than a million million, many years ago, you would say:
One hundred and seventy two billion one hundred and forty seven million one hundred and twenty two point two five.
Using "a" in place on the "one" is acceptable in any or all cases.
"and a quarter" is acceptable in place of "point two five", but not "point a quarter". 'point twenty five' is also mathematically wrong, not just wrong in English.
Regarding "million" and "billion", it might be worth learning about "long count" and "short count". Those, as well as larger numbers, such as "trillion", etc. had different meanings in the two counting systems.
For instance, in the long count system, a billion is a million million, as stated, and what users of the short count system call a billion (a thousand million), the long count users might call a "milliard". There's also a "billiard", extremely likely having no connection at all to the game with that name.
Various different nations use one of these schemes, long or short. If one is a translator, or involved in finance, one must beware of assuming the wrong system to be in use!
Those who have listened to the BBC's American service for a long time would probably remember their usage of "thousand million". Perhaps they considered "milliard" to be confoundingly obscure to us. Apparently, Great Bnitain used the long count, but changed to short count to accommodate U.S. listeners, because we use the short count. (They also no longer use "lorry", which we know as "truck".)
I apologize for providing no refs., but Wikipedia is probably a good source, and "long count" should be a good search term.
It might be that long count is becoming obsolescent, but with the number of nations in the world, one can't be sure. There has been at least some general advice, if not a comprehensive list of who uses which.
India has traditionally dealt with large numbers in its own way. They apparently freely use the terms "lakh" and "crore" for fairly large numbers, but neither is a multiple of 1,000. "Lakh" might be 100,000, and "crore" 10,000,000, but don't assume that to be correct.
Moreover, their traditional system of grouping ("pointing off") quite large numbers is complex. One grouping would be 1,000,00. if I recall correctly. That just might be their traditional way of writing a lakh. I don't recall anything regarding decimal fractions.