# How do you write 21,900,000,000 in scientific notation?

$21 , 900 , 000 , 000 = 2.19 \cdot {10}^{10}$
You have to take the first significative digit from the left of the number, put a comma and the multiply by ${10}^{n}$ where $n$ is the number of digits on the right until the end of the number or until a comma.