We divide 25512889 by 21
We want to figure out the number of times 25512889 can be divided by 21.

Advancing to step 1:
2 divided by 21 is 0 with a remainder of 2.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 2, we get 2.
Fetch the next digit (5) from the dividend, attach it to 2 and continue: 25 / 21

Let's proceed to step 2:
21 goes into 25 1 times with a remainder of 4.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
Subtract 21 from 25 to get 4.
Include the next digit (5) from the dividend after 4, then repeat: 45 / 21

Moving on to step 3:
45 divided by 21 is 2 with a remainder of 3.
Record the quotient 2 as the next digit in the result. 
Result so far: 12.0
Subtract 42 from 45 to get 3.
Bring next digit (1) of the dividend behind the 3 and repeat the process: 31 / 21

On to step 4:
21 goes into 31 1 times with a remainder of 10.
Record the quotient 1 as the next digit in the result. 
Result so far: 121.0
Subtracting 21 from 31 leaves us with 10.
Fetch the next digit (2) from the dividend, attach it to 10 and continue: 102 / 21

Going ahead to step 5:
21 can be fit into 102 4 times, resulting in a remainder of 18.
Write down 4 as next digit of the result. 
Result so far: 1214.0
Deduct 84 from 102 and we're left with 18.
Include the next digit (8) from the dividend after 18, then repeat: 188 / 21

Let's proceed to step 6:
188 divided by 21 is 8 with a remainder of 20.
The next digit of our result is 8. 
Result so far: 12148.0
Deduct 168 from 188 and we're left with 20.
Grab the next digit (8) from the dividend, add it to 20, then carry on: 208 / 21

On to step 7:
The number 21 fits into 208 9 times, leaving a remainder of 19.
Put 9 as the next digit of the answer. 
Result so far: 121489.0
If we take 189 away from 208, we end up with 19.
Bring next digit (9) of the dividend behind the 19 and repeat the process: 199 / 21

Step 8:
21 can be fit into 199 9 times, resulting in a remainder of 10.
The number 9 becomes the next digit in our result. 
Result so far: 1214899.0
Deduct 189 from 199 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Let's proceed to step 9:
21 goes into 100 4 times with a remainder of 16.
Record the quotient 4 as the next digit in the result. 
Result so far: 1214899.4
If we subtract 84 from 100, we get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Step 10:
21 can be fit into 160 7 times, resulting in a remainder of 13.
Record the quotient 7 as the next digit in the result. 
Result so far: 1214899.47
The remainder is 13 after subtracting 147 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Moving on to step 11:
21 goes into 130 6 times with a remainder of 4.
The number 6 becomes the next digit in our result. 
Result so far: 1214899.476
If we take 126 away from 130, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Step 12:
When dividing 40 by 21, we get 1 with a remainder of 19.
The next digit of our result is 1. 
Result so far: 1214899.4761
If we take 21 away from 40, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Let's proceed to step 13:
21 can be fit into 190 9 times, resulting in a remainder of 1.
Use 9 as the next digit of our solution. 
Result so far: 1214899.47619
Subtracting 189 from 190 leaves us with 1.
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:
21 goes into 10 0 times with a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 1214899.47619
If we subtract 0 from 10, we 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.

Moving on to step 15:
100 divided by 21 is 4 with a remainder of 16.
Put 4 as the next digit of the answer. 
Result so far: 1214899.4761904
If we take 84 away from 100, we end up with 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Going ahead to step 16:
21 can be fit into 160 7 times, resulting in a remainder of 13.
The number 7 becomes the next digit in our result. 
Result so far: 1214899.47619047
The remainder is 13 after subtracting 147 from 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

The final outcome is 1214899.47619047, with a leftover of 1.3e-08.