400946 ÷ 21 
Let's see how many times 21 fits into 400946.

Let's proceed to step 1:
The number 21 fits into 4 0 times, leaving a remainder of 4.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 4, we get 4.
Include the next digit (0) from the dividend after 4, then repeat: 40 / 21

Advancing to step 2:
When dividing 40 by 21, we get 1 with a remainder of 19.
Use 1 as the next digit of our solution. 
Result so far: 1.0
The remainder is 19 after subtracting 21 from 40.
Append the next digit (0) from the dividend to 19 and continue with: 190 / 21

Advancing to step 3:
The number 21 fits into 190 9 times, leaving a remainder of 1.
The next digit of our result is 9. 
Result so far: 19.0
The remainder is 1 after subtracting 189 from 190.
Append the next digit (9) from the dividend to 1 and continue with: 19 / 21

On to step 4:
19 divided by 21 is 0 with a remainder of 19.
The number 0 becomes the next digit in our result. 
Result so far: 190.0
Subtract 0 from 19 to get 19.
Take the next digit (4) from the dividend and append it to 19, then repeat: 194 / 21

Advancing to step 5:
194 divided by 21 is 9 with a remainder of 5.
The number 9 becomes the next digit in our result. 
Result so far: 1909.0
If we subtract 189 from 194, we get 5.
Append the next digit (6) from the dividend to 5 and continue with: 56 / 21

On to step 6:
56 divided by 21 is 2 with a remainder of 14.
The next digit of our result is 2. 
Result so far: 19092.0
If we subtract 42 from 56, we get 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Advancing to step 7:
When dividing 140 by 21, we get 6 with a remainder of 14.
Write down 6 as next digit of the result. 
Result so far: 19092.6
The remainder is 14 after subtracting 126 from 140.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Let's proceed to step 8:
21 goes into 140 6 times with a remainder of 14.
Record the quotient 6 as the next digit in the result. 
Result so far: 19092.66
Subtracting 126 from 140 leaves us with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

After the division, we end up with 19092.66 and a remainder of 0.014.