Find the Outlier: Which Number Doesn't Belong in 23, 27, 21, 32?

To solve this problem, we'll follow these steps:

• Step 1: Identify if each given number is odd or even.

• Step 2: Compare and determine the number with the different characteristic.

• Step 3: Conclude the analysis with the number that is distinct.

Now, let's work through each step:
Step 1: Check if each number is odd or even by checking divisibility by 2.
- 23: Dividing by 2 gives a remainder, hence it is odd.
- 27: Dividing by 2 gives a remainder, so it is also odd.
- 21: Dividing by 2 results in a remainder, thus it is odd.
- 32: Dividing by 2 gives no remainder, therefore it is even.

Step 2: Compare the results:
Three numbers (23, 27, 21) are odd, while one number (32) is even.

Therefore, the solution to the problem is $32$.