Odd man out: Find the odd man out. 7, 13, 19, 25, 29, 37, 43

Concept

In an “odd man out” number series, every term except one satisfies a shared classification rule; the term that breaks the rule is the answer. Here the natural classification is by primality — a prime number has exactly two divisors (1 and itself), while a composite number has more than two divisors.

Application

Check every term in the sequence for primality:

Cross-check

Six of the seven terms — 7, 13, 19, 29, 37, and 43 — are prime, following the same rule. Only 25 breaks that rule, since 5 × 5 = 25 gives it a third divisor. So 25 is the odd man out.