The question asks to "Find the odd one out in the set: {19, 37, 21, 17, 23, 29, 31, 11}."

Looking at this set, all the numbers except one are prime numbers. A prime number is a number greater than 1 that has no positive divisors other than 1 and itself.

• 19: Prime
• 37: Prime
• 21: Not prime (It is divisible by 3 and 7)
• 17: Prime
• 23: Prime
• 29: Prime
• 31: Prime
• 11: Prime

The number 21 is the only non-prime number in the set, making it the odd one out.

Would you like further details on prime numbers or other related concepts?

Here are 5 related questions to explore:

1. What is the definition of prime numbers and how are they determined?
2. Can you find the prime numbers between 50 and 100?
3. What is the significance of prime numbers in mathematics?
4. How do you determine if a large number is prime?
5. What are twin primes and how do they relate to the numbers in this set?

Tip: To check if a number is prime, try dividing it by all prime numbers less than its square root. If it's divisible by any, it's not prime.