The next prime number after 19 is 23.

Would you like more details on how prime numbers are determined, or do you have any other questions?

Here are 5 related questions for deeper exploration:

1. What are the prime numbers between 1 and 50?
2. How can you determine if a large number is prime?
3. What is the significance of prime numbers in cryptography?
4. Can prime numbers form a pattern, or are they randomly distributed?
5. What is the largest known prime number?

Tip: A prime number is a number greater than 1 that has no divisors other than 1 and itself.