Answer: 6,611
Start from the right most digit. Then move your way to the left. Each time you hit 3 digits, you put a comma. The comma separates out every 3 digits.
Here are some other examples
- 1656 = 1,656
- 38880 = 38,880
- 660960 = 660,960
- 1234567 = 1,234,567
- 11897280 = 11,897,280