815,642,120 in words is Eight hundred fifteen million, six hundred forty-two thousand, one hundred twenty.
To break it down:
- The first part, Eight hundred fifteen million, comes from the 815 in the millions place.
- The next part, Six hundred forty-two thousand, is derived from the 642 in the thousands place.
- Finally, the one hundred twenty represents the last three digits, which are 120.
Putting it all together, we clearly articulate the number as a whole, ensuring that each segment of the number is represented accurately in words, following the conventions of the international number system.