In natural numbers 20 ~ 30, even numbers have (); odd numbers have (); prime numbers have (); and sum numbers have ()

In natural numbers 20 ~ 30, even numbers have (); odd numbers have (); prime numbers have (); and sum numbers have ()

In natural numbers 20 ~ 30, even numbers have (20,22,24,26,28,30); odd numbers have (21,23,25,27,29); prime numbers have (23,29); sum numbers have (20,21,22,24,25,26,27,28,30)

Given that a is prime, B is odd, and a ^ 2 + B = 2001, find the value of a + B
Please state the process

Since 2001 and B are odd numbers, a ^ 2 must be even, then a is even, but a is prime, and the only even prime is 2
a=2
Then the known equation becomes:
4+b=2001
b=1997
So:
a+b
=2+1997
=1999

Product of multiplication of two prime numbers ()
A. It must be prime B. it must be odd C. It must be even D. It must be composite

In addition to 1 and itself, the factor of the product of two prime numbers also has these two factors. According to the meaning of composite number, the product of two prime numbers must be composite number

The product of two continuous natural numbers must be (). 1 prime number 2 composite number 3 odd number 4 even number

Even number
Because two consecutive natural numbers must have an even number and an odd number
Then the product must be even