1. **State the problem:** Calculate the sum of 1 and 21. 2. **Formula used:** Addition of two numbers is given by $a + b$. 3. **Apply the formula:** Here, $a = 1$ and $b = 21$, so we calculate: $$1 + 21$$ 4. **Perform the addition:** $$1 + 21 = 22$$ 5. **Final answer:** The sum of 1 and 21 is **22**.