Of the numbers 26, 34, 62 and 72, three share a property that the fourth lacks. Choose the odd one out.

Multiply the two digits of each number: $2\times 6=12,3\times 4=12$ and $6\times 2=12$, but $7\times 2=14$, so 72 alone fails. A second reading gives the same answer: 26, 34 and 62 are each twice a prime, being $2\times 13,2\times 17$ and $2\times 31$, while 72 is $8\times 9$.