No, it is not necessary.
There are exactly as many odd numbers as primes (Euclid, Cantor), and exactly one even prime (namely 2), so there must be exactly one odd nonprime (namely 1). Cosmologist: 3 is prime, yes it is true.... ... 10 is prime, 11 is prime, 101 is prime...
And one even number is prime---see Rooster's answer.
No, it's not necessary. The number only divisible by 1 and itself is prime number.