21123690 ÷ 251 
We want to figure out the number of times 21123690 can be divided by 251.

Advancing to step 1:
2 divided by 251 is 0 with a remainder of 2.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 2 after subtracting 0 from 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 251

Step 2:
The number 251 fits into 21 0 times, leaving a remainder of 21.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 21 after subtracting 0 from 21.
Fetch the next digit (1) from the dividend, attach it to 21 and continue: 211 / 251

Going ahead to step 3:
When dividing 211 by 251, we get 0 with a remainder of 211.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we take 0 away from 211, we end up with 211.
Grab the next digit (2) from the dividend, add it to 211, then carry on: 2112 / 251

Moving on to step 4:
251 can be fit into 2112 8 times, resulting in a remainder of 104.
Record the quotient 8 as the next digit in the result. 
Result so far: 8.0
Deduct 2008 from 2112 and we're left with 104.
Bring next digit (3) of the dividend behind the 104 and repeat the process: 1043 / 251

Moving on to step 5:
251 can be fit into 1043 4 times, resulting in a remainder of 39.
Put 4 as the next digit of the answer. 
Result so far: 84.0
Subtracting 1004 from 1043 leaves us with 39.
Take the next digit (6) from the dividend and append it to 39, then repeat: 396 / 251

Moving on to step 6:
When dividing 396 by 251, we get 1 with a remainder of 145.
The number 1 becomes the next digit in our result. 
Result so far: 841.0
The remainder is 145 after subtracting 251 from 396.
Bring next digit (9) of the dividend behind the 145 and repeat the process: 1459 / 251

Step 7:
251 goes into 1459 5 times with a remainder of 204.
Use 5 as the next digit of our solution. 
Result so far: 8415.0
Subtracting 1255 from 1459 leaves us with 204.
Append the next digit (0) from the dividend to 204 and continue with: 2040 / 251

Moving on to step 8:
251 goes into 2040 8 times with a remainder of 32.
Put 8 as the next digit of the answer. 
Result so far: 84158.0
If we take 2008 away from 2040, we end up with 32.
Since there are no more digits in the dividend, we add a zero to the remainder making it 320, and continue the process.

Moving on to step 9:
When dividing 320 by 251, we get 1 with a remainder of 69.
The number 1 becomes the next digit in our result. 
Result so far: 84158.1
The remainder is 69 after subtracting 251 from 320.
Since there are no more digits in the dividend, we add a zero to the remainder making it 690, and continue the process.

On to step 10:
251 goes into 690 2 times with a remainder of 188.
The next digit of our result is 2. 
Result so far: 84158.12
If we subtract 502 from 690, we get 188.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1880, and continue the process.

On to step 11:
251 can be fit into 1880 7 times, resulting in a remainder of 123.
The next digit of our result is 7. 
Result so far: 84158.127
The remainder is 123 after subtracting 1757 from 1880.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1230, and continue the process.

Let's proceed to step 12:
251 goes into 1230 4 times with a remainder of 226.
Use 4 as the next digit of our solution. 
Result so far: 84158.1274
If we take 1004 away from 1230, we end up with 226.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2260, and continue the process.

On to step 13:
When dividing 2260 by 251, we get 9 with a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 84158.12749
The remainder is 1 after subtracting 2259 from 2260.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Going ahead to step 14:
If we divide 10 by 251, we get 0 and a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 84158.12749
Subtract 0 from 10 to get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Step 15:
251 goes into 100 0 times with a remainder of 100.
Write down 0 as next digit of the result. 
Result so far: 84158.12749
Deduct 0 from 100 and we're left with 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1000, and continue the process.

In conclusion, the division gives 84158.12749 with a balance of 1e-06.