Do the numerator and denominator of the simplest fraction have to be two numbers of prime numbers?
The numerator and denominator of the simplest fraction are coprime. There are two concepts here that cannot be confused. The concept of prime number, prime number. Prime number is a number, and coprime number is the relationship between two numbers, not a number. Maybe two numbers are prime numbers (2,3), maybe two numbers are composite numbers (4,9), maybe one is prime number and the other is composite number (3,4).