We look at the division of 780590 by 21 
We're looking to find how many times 21 goes into 780590.

Step 1:
The number 21 fits into 7 0 times, leaving a remainder of 7.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 7 after subtracting 0 from 7.
Include the next digit (8) from the dividend after 7, then repeat: 78 / 21

Step 2:
If we divide 78 by 21, we get 3 and a remainder of 15.
The next digit of our result is 3. 
Result so far: 3.0
If we subtract 63 from 78, we get 15.
Bring next digit (0) of the dividend behind the 15 and repeat the process: 150 / 21

Step 3:
21 goes into 150 7 times with a remainder of 3.
Record the quotient 7 as the next digit in the result. 
Result so far: 37.0
The remainder is 3 after subtracting 147 from 150.
Append the next digit (5) from the dividend to 3 and continue with: 35 / 21

Moving on to step 4:
The number 21 fits into 35 1 times, leaving a remainder of 14.
Record the quotient 1 as the next digit in the result. 
Result so far: 371.0
Subtract 21 from 35 to get 14.
Append the next digit (9) from the dividend to 14 and continue with: 149 / 21

Going ahead to step 5:
The number 21 fits into 149 7 times, leaving a remainder of 2.
Use 7 as the next digit of our solution. 
Result so far: 3717.0
If we subtract 147 from 149, we get 2.
Grab the next digit (0) from the dividend, add it to 2, then carry on: 20 / 21

On to step 6:
21 goes into 20 0 times with a remainder of 20.
Put 0 as the next digit of the answer. 
Result so far: 37170.0
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Let's proceed to step 7:
If we divide 200 by 21, we get 9 and a remainder of 11.
Use 9 as the next digit of our solution. 
Result so far: 37170.9
Subtracting 189 from 200 leaves us 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.

On to step 8:
The number 21 fits into 110 5 times, leaving a remainder of 5.
Use 5 as the next digit of our solution. 
Result so far: 37170.95
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.

Step 9:
50 divided by 21 is 2 with a remainder of 8.
Use 2 as the next digit of our solution. 
Result so far: 37170.952
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.

Advancing to step 10:
80 divided by 21 is 3 with a remainder of 17.
Put 3 as the next digit of the answer. 
Result so far: 37170.9523
Deduct 63 from 80 and we're left with 17.
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 11:
170 divided by 21 is 8 with a remainder of 2.
Use 8 as the next digit of our solution. 
Result so far: 37170.95238
Subtract 168 from 170 to 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 12:
When dividing 20 by 21, we get 0 with a remainder of 20.
The next digit of our result is 0. 
Result so far: 37170.95238
The remainder is 20 after subtracting 0 from 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Advancing to step 13:
21 can be fit into 200 9 times, resulting in a remainder of 11.
The number 9 becomes the next digit in our result. 
Result so far: 37170.9523809
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.

Moving on to step 14:
When dividing 110 by 21, we get 5 with a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 37170.95238095
The remainder is 5 after subtracting 105 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

The final outcome is 37170.95238095, with a leftover of 5e-09.