In words, 999,999,999 is nine hundred ninety-nine million nine hundred ninety-nine thousand nine hundred ninety-nine.
When you write a long number, you use commas to separate periods. Periods are simply groups of three numbers. They help make long numbers more readable. For example, here’s about as long a number as you’ll ever see: 234,845,021,349,230,467,304.
The following list breaks this number down into periods.
Quintillions 234
Quadrillions 845
Trillions 021
Billions 349
Millions 230
Thousands 467
Ones 304
Find out how to say and spell really huge numbers using Math Cats' Really Big Numbers converter tool.