Find the number of unique Prime factors of 210.

Explanation

To find the number of unique prime factors of 210, we will perform the prime factorization step by step.

### Step 1: Start with the number
We begin with the number 210.

### Step 2: Divide by the smallest prime number
The smallest prime number is 2. We check if 210 is divisible by 2:
- 210 ÷ 2 = 105
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