515960 divided by 21 
We want to figure out the number of times 515960 can be divided by 21.

Step 1:
When dividing 5 by 21, we get 0 with a remainder of 5.
The next digit of our result is 0. 
Result so far: 0.0
The remainder is 5 after subtracting 0 from 5.
Bring next digit (1) of the dividend behind the 5 and repeat the process: 51 / 21

Moving on to step 2:
The number 21 fits into 51 2 times, leaving a remainder of 9.
Write down 2 as next digit of the result. 
Result so far: 2.0
The remainder is 9 after subtracting 42 from 51.
Grab the next digit (5) from the dividend, add it to 9, then carry on: 95 / 21

Moving on to step 3:
21 can be fit into 95 4 times, resulting in a remainder of 11.
Write down 4 as next digit of the result. 
Result so far: 24.0
Subtracting 84 from 95 leaves us with 11.
Take the next digit (9) from the dividend and append it to 11, then repeat: 119 / 21

Advancing to step 4:
21 can be fit into 119 5 times, resulting in a remainder of 14.
Write down 5 as next digit of the result. 
Result so far: 245.0
Subtracting 105 from 119 leaves us with 14.
Append the next digit (6) from the dividend to 14 and continue with: 146 / 21

Going ahead to step 5:
146 divided by 21 is 6 with a remainder of 20.
Use 6 as the next digit of our solution. 
Result so far: 2456.0
If we take 126 away from 146, we end up with 20.
Append the next digit (0) from the dividend to 20 and continue with: 200 / 21

Advancing to step 6:
21 goes into 200 9 times with a remainder of 11.
Record the quotient 9 as the next digit in the result. 
Result so far: 24569.0
If we subtract 189 from 200, we get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Let's proceed to step 7:
110 divided by 21 is 5 with a remainder of 5.
The next digit of our result is 5. 
Result so far: 24569.5
Subtracting 105 from 110 leaves us with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

On to step 8:
50 divided by 21 is 2 with a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 24569.52
The remainder is 8 after subtracting 42 from 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

On to step 9:
80 divided by 21 is 3 with a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 24569.523
The remainder is 17 after subtracting 63 from 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Going ahead to step 10:
170 divided by 21 is 8 with a remainder of 2.
Write down 8 as next digit of the result. 
Result so far: 24569.5238
If we subtract 168 from 170, we get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Going ahead to step 11:
20 divided by 21 is 0 with a remainder of 20.
Record the quotient 0 as the next digit in the result. 
Result so far: 24569.5238
Subtract 0 from 20 to get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 12:
If we divide 200 by 21, we get 9 and a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 24569.523809
Deduct 189 from 200 and we're left with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Going ahead to step 13:
110 divided by 21 is 5 with a remainder of 5.
Write down 5 as next digit of the result. 
Result so far: 24569.5238095
If we subtract 105 from 110, we get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Moving on to step 14:
When dividing 50 by 21, we get 2 with a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 24569.52380952
If we subtract 42 from 50, we get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

The final outcome is 24569.52380952, with a leftover of 8e-09.