How many significant figures in 4.020×10^6

Three significant digits are present.

Explanation:

4.020×10⁶ = 4,020,000

So  the number of significant figures are three.

Significant figures:

The given measurement have four significant figures 1234.

All non-zero digits are consider significant figures like 1, 2, 3, 4, 5, 6, 7, 8, 9.

Leading zeros are not consider as a significant figures. e.g. 0.03 in this number only one significant figure present which is 3.

Zero between the non zero digits are consider significant like 104 consist of three significant figures.

If a number have decimal point then trailing zero will be a significant. like 78600 have three significant digit while the number 78600. have five significant digit.

In given number 4020,000 only three significant digit present 4, 0 and 2.