1. **State the problem:** We need to determine if 23 is a factor of 851. 2. **Recall the definition:** A number $a$ is a factor of $b$ if $b$ divided by $a$ results in an integer with no remainder. 3. **Apply the division:** Calculate $\frac{851}{23}$. 4. **Perform the division:** $$\frac{851}{23} = 37$$ 5. **Interpret the result:** Since 37 is an integer and there is no remainder, 23 is indeed a factor of 851. **Final answer:** Yes, 23 is a factor of 851.