To solve this question, we need to identify the region in the diagram that represents Men who are both Businessmen and Millionaires. Let's analyze the Venn diagram:

1. The triangle represents Men.
2. The rectangle represents Businessmen.
3. The circle represents Millionaires.

We are looking for the number that lies in the intersection of all three shapes (triangle, circle, and rectangle). This represents Men who are both Businessmen and Millionaires.

Observing the diagram:

• The number 10 is located inside the triangle (Men), rectangle (Businessmen), and circle (Millionaires).

Therefore, the correct answer is 10.

Let's rule out the other options:

• Number 12 is only in the intersection of Men and Businessmen, not Millionaires.
• Number 11 is only in the region of Businessmen.
• Number 13 is only in the region of Men.

Thus, the number representing Men that are both Businessmen and Millionaires is accurately 10.