no, not all prime numbers are closed under addition. why? because, when you add 2 prime numbers you will not always get a prime number. example: 5+3= 8 5 and 3 are prime numbers but their sum is 8 which is a composite number..
No. The product of two primes cannot, by definition, be a prime.
No, they are not. You can add two composite numbers, 15 and 14 for example, and get a sum, 29, that is prime.
The set of even numbers is closed under addition, the set of odd numbers is not.
By definition, a product of two primes has atwo factors (other than 1 and itself) and so it cannot be prime. So the set is not closed.
The numbers are not closed under addition because whole numbers, even integers, and natural numbers are closed.
Prime Numbers under 6 are 2,3,5
There are 34 prime numbers under 140.