258791 divided by 21 
We're looking to find how many times 21 goes into 258791.

Going ahead to step 1:
The number 21 fits into 2 0 times, leaving a remainder of 2.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 2 leaves us with 2.
Fetch the next digit (5) from the dividend, attach it to 2 and continue: 25 / 21

Going ahead to step 2:
If we divide 25 by 21, we get 1 and a remainder of 4.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
If we take 21 away from 25, we end up with 4.
Take the next digit (8) from the dividend and append it to 4, then repeat: 48 / 21

Let's proceed to step 3:
When dividing 48 by 21, we get 2 with a remainder of 6.
The next digit of our result is 2. 
Result so far: 12.0
If we subtract 42 from 48, we get 6.
Fetch the next digit (7) from the dividend, attach it to 6 and continue: 67 / 21

On to step 4:
The number 21 fits into 67 3 times, leaving a remainder of 4.
The next digit of our result is 3. 
Result so far: 123.0
Deduct 63 from 67 and we're left with 4.
Include the next digit (9) from the dividend after 4, then repeat: 49 / 21

Advancing to step 5:
49 divided by 21 is 2 with a remainder of 7.
The number 2 becomes the next digit in our result. 
Result so far: 1232.0
Deduct 42 from 49 and we're left with 7.
Fetch the next digit (1) from the dividend, attach it to 7 and continue: 71 / 21

Advancing to step 6:
When dividing 71 by 21, we get 3 with a remainder of 8.
Record the quotient 3 as the next digit in the result. 
Result so far: 12323.0
Deduct 63 from 71 and we're left with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Moving on to step 7:
80 divided by 21 is 3 with a remainder of 17.
Record the quotient 3 as the next digit in the result. 
Result so far: 12323.3
Subtract 63 from 80 to get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Let's proceed to step 8:
21 goes into 170 8 times with a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 12323.38
Subtracting 168 from 170 leaves us with 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 9:
When dividing 20 by 21, we get 0 with a remainder of 20.
The next digit of our result is 0. 
Result so far: 12323.38
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.

Moving on to step 10:
The number 21 fits into 200 9 times, leaving a remainder of 11.
Use 9 as the next digit of our solution. 
Result so far: 12323.3809
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.

Going ahead to step 11:
If we divide 110 by 21, we get 5 and a remainder of 5.
Use 5 as the next digit of our solution. 
Result so far: 12323.38095
Deduct 105 from 110 and we're left 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 12:
21 can be fit into 50 2 times, resulting in a remainder of 8.
The number 2 becomes the next digit in our result. 
Result so far: 12323.380952
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.

Step 13:
If we divide 80 by 21, we get 3 and a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 12323.3809523
If we subtract 63 from 80, we get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Advancing to step 14:
21 can be fit into 170 8 times, resulting in a remainder of 2.
Use 8 as the next digit of our solution. 
Result so far: 12323.38095238
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.

In conclusion, the division gives 12323.38095238 with a balance of 2e-09.