What is 16,700,000,000,000,000 estimated as the product of a single digit and a power of 10?

First, the number of zeros you have is the power of 10 and as a product, it would look like:

167*10^14.

But we need a number with a single digit which means we have to divide 167 by 100=10^2. In order to have the same equation, we need also to multiply by 10^2. Now it would look like:

1.67 * 10^14 * 10^2 = 1.67 * 10^16

Now 1.67 rounded up is 2. The final solution is:

2 * 10^16