78451 ÷ 2 = 39225 R1
Let's divide 78451 by 2.

Step 1:
2 goes into 7 3 times with a remainder of 1.
Write down 3 as next digit of of the result. 
Result so far: 3
Subtract 6 from 7 to get 1.
Bring next digit (8) of the dividend behind the 1 and repeat the process: 18 / 2

Step 2:
2 goes into 18 9 times with a remainder of 0.
Write down 9 as next digit of of the result. 
Result so far: 39
Subtract 18 from 18 to get 0.
Bring next digit (4) of the dividend behind the 0 and repeat the process: 4 / 2

Step 3:
2 goes into 4 2 times with a remainder of 0.
Write down 2 as next digit of of the result. 
Result so far: 392
Subtract 4 from 4 to get 0.
Bring next digit (5) of the dividend behind the 0 and repeat the process: 5 / 2

Step 4:
2 goes into 5 2 times with a remainder of 1.
Write down 2 as next digit of of the result. 
Result so far: 3922
Subtract 4 from 5 to get 1.
Bring next digit (1) of the dividend behind the 1 and repeat the process: 11 / 2

Step 5:
2 goes into 11 5 times with a remainder of 1.
Write down 5 as next digit of of the result. 
Result so far: 39225
Subtract 10 from 11 to get 1.

The final result is 39225 with a remainder of 1.