Find the odd number out in the sequence: 3, 5, 11, 14, 17, 21.

Problem restatement
Identify the single term that does not follow the same basic property as the others in the list 3, 5, 11, 14, 17, 21.

Given data

• Sequence: 3, 5, 11, 14, 17, 21
• Task: Find the one number that differs in a simple, common property.

Concept / Approach
Start with the simplest structural checks: parity (odd/even), perfect squares/cubes, small prime/composite patterns, and quick divisibility. The simplest clear separator here is parity.

Step-by-step check
3 → odd 5 → odd 11 → odd 14 → even 17 → odd 21 → odd

Exactly one term (14) is even; all others are odd.

Verification / Alternative
Prime/composite is not decisive here (21 and 14 are composite, others are prime), but parity produces a unique outlier: only 14 is even.

Common pitfalls

• Overfitting: trying to impose a complex pattern when a basic property (odd/even) already yields a unique answer.
• Mixing prime vs composite leads to two composites (14 and 21), not a single outlier.

Final Answer
14