Sixteen quintillion
Here's the breakdown:
* 6,240,000,000,000,000,000: This number is read as six quadrillion, two hundred forty trillion.
* Quintillion: This is the name for the number 1,000,000,000,000,000,000 (a one followed by 18 zeros).
So, you can either say "six quadrillion, two hundred forty trillion" or the shorter "sixteen quintillion".