9. (6 points) A certain day in February is a Sunday. On this day, three groups of students visited Teacher Li, and the number of students in each group was different, and no one visited the teacher alone. The product of the number of students in these three groups is exactly equal to the date of this day. Then, February 1st is a $\qquad$

保留源文本的换行和格式，直接输出翻译结果。
9. (6 points) A certain day in February is a Sunday. On this day, three groups of students visited Teacher Li, and the number of students in each group was different, and no one visited the teacher alone. The product of the number of students in these three groups is exactly equal to the date of this day. Then, February 1st is a $\qquad$.

【Solution】Solution: The number of students in the three groups are: $2, 3, 4$, because $2 \times 3 \times 4=24$, so this day is February 24th, and since February 24th is a Sunday,

it can be deduced that February 3rd is a Sunday, and further deduced that February 1st is a Friday.
Therefore, the answer is: Friday.