Answer:
At least 35 years old.
Step-by-step explanation:
Article two of the United States Constitution explains how the Executive Branch is formed, how the president is elected and the qualifications needed to become President of the United States.
On clause 5, it states the minimum age, 35 and it must be a natural-born citizen and have lived in the country for 14 years as a minimum.
I hope this answer helps you.