We look at the division of 790573 by 21 
Let's see how many times 21 fits into 790573.

On to step 1:
21 can be fit into 7 0 times, resulting in a remainder of 7.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 7 leaves us with 7.
Include the next digit (9) from the dividend after 7, then repeat: 79 / 21

Step 2:
21 can be fit into 79 3 times, resulting in a remainder of 16.
Put 3 as the next digit of the answer. 
Result so far: 3.0
If we subtract 63 from 79, we get 16.
Bring next digit (0) of the dividend behind the 16 and repeat the process: 160 / 21

Going ahead to step 3:
When dividing 160 by 21, we get 7 with a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 37.0
Subtract 147 from 160 to get 13.
Include the next digit (5) from the dividend after 13, then repeat: 135 / 21

Moving on to step 4:
21 can be fit into 135 6 times, resulting in a remainder of 9.
Use 6 as the next digit of our solution. 
Result so far: 376.0
Subtracting 126 from 135 leaves us with 9.
Include the next digit (7) from the dividend after 9, then repeat: 97 / 21

On to step 5:
The number 21 fits into 97 4 times, leaving a remainder of 13.
Record the quotient 4 as the next digit in the result. 
Result so far: 3764.0
Deduct 84 from 97 and we're left with 13.
Bring next digit (3) of the dividend behind the 13 and repeat the process: 133 / 21

Moving on to step 6:
21 goes into 133 6 times with a remainder of 7.
Use 6 as the next digit of our solution. 
Result so far: 37646.0
If we subtract 126 from 133, we get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Going ahead to step 7:
21 can be fit into 70 3 times, resulting in a remainder of 7.
Write down 3 as next digit of the result. 
Result so far: 37646.3
Deduct 63 from 70 and we're left with 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Step 8:
When dividing 70 by 21, we get 3 with a remainder of 7.
Write down 3 as next digit of the result. 
Result so far: 37646.33
Subtract 63 from 70 to get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

The quotient of the division is 37646.33, and the remainder is 0.007.