Find the odd one out among the following numbers.

1. Check each for being a perfect square: 169 = 13², 121 = 11², 144 = 12². 2. For 181, note 13² = 169 and 14² = 196, so 181 is not a perfect square. 3. Therefore 181 is the odd one out. _Source: RRB Group D (RRC) PYQ, held 27-10-2013, Q.87._