Find the odd number / letters / word from the given alternative:

17
27
29
37 E. 59

The odd number in the given list is 27. All the other numbers are prime numbers, while 27 is a composite number. A prime number is a natural number greater than 1 that is not a product of two smaller natural numbers. A composite number is a natural number greater than 1 that is not prime.

17, 37, and 59 are all prime numbers because they are only divisible by 1 and themselves. 27 is a composite number because it is divisible by 1, 3, 9, and 27.