How many even $4$- digit integers are there whose digits are distinct?
We have two restrictions here: the first digit cannot be $0$ and the last digit must be even.
Solution 1
We first choose the first digit, then the last digit, afterwards the second and the third digit. However, because $0$ is an even digit itself but cannot be placed as the first, we need to do a casework:
last digit is $0$:
last digit is not $0$:
Hence the answerr is $1\times 9 \times 8\times 7 + 4\times 8\times 8\times 7 = \boxed{2296}$.
Solutions 2
Alternatively, we can also employ the count the opposite technique because counting odd number is easier.
Therefore, the number of odd integers: $4536-2240 =2296$.