Write 2E21 in decimal notation.

Step 1: Since 2 do not have a decimal point, we will add one at the end of the number 2.

2.

Step 2: The exponent for 10 is 21. Since the exponent is positive, we must move the decimal point of a number 2. 21 places to the right.

2. → 2.---------------------.

Step 3: Now we just need to replace empty spaces (dashes) with zeros and to delete old decimal point (the black one) to get:

2000000000000000000000