Zero.
No, the sum of a prime number and a composite number is not always even.
Two odd numbers always sum to an even number. Always. Two even numbers always sum to an even number, and an odd number and an even number always sum to an odd number.
Because the sum of two odd numbers is always even and the sum of that even number plus another odd number is always odd.
The sum of two odd numbers is always even.
Yes, always.
Such a sum is always irrational.
The sum of two odd primes is always an even answer or number.
The sum of any two prime numbers is not always a composite number. The sum of 2 and 11 is 13, and 13 is a prime number, not a composite number.
Not always, if the smaller number is 0 or a negative number. Then their sum will be equal or less than the greater number.
No
No
No.