Identify the odd number: In the set 13, 43, 63, 23, three are prime and one is composite. Choose the composite number.

Introduction / Context:
This classification checks prime recognition among small integers. Only one option is composite, which makes it the odd one out.

Given Data / Assumptions:

• Numbers: 13, 43, 63, 23.
• Prime: exactly two divisors.
• Composite: more than two divisors.

Concept / Approach:
Use quick tests: even > 2 → composite; ends with 5 and > 5 → composite; digit sum multiple of 3 → divisible by 3 → composite. Confirm remaining suspects with small primes.

Step-by-Step Solution:

Verification / Alternative check:
Direct division by 7 shows 63 = 7 * 9 as well, reinforcing composite status.

Why Other Options Are Wrong:
13, 43, and 23 are prime and consistent with the majority property.

Common Pitfalls:
Confusing large-looking numbers (like 43) as composite; always apply divisibility tests.

Final Answer:
63 is composite and hence the odd number.