is no 1 a prime no?

Answer 1

NO. 1 is NOT a prime number.

This question comes up a lot and some people actually say "yes", but they're dead wrong. 1 is neither prime nor composite. Prime numbers have exactly two factors, and composite numbers have more than two. 1 only has one unique factor, "1".

If you need more convincing, go here:
http://mathforum.org/library/drmath/view/57058.html

Answer 2

It's a convention, and it could have gone the other way, but there are good reasons for this choice. Basically, people looked at their theorems and realized that 1 would be a special case in many propositions involving primes. Suppose 1 were a prime. Here are a couple consequences.

1) Every prime integer p is divisible by another prime integer, 1. This is an undesirable property for a prime to have. It does not mesh with our intuition of primes.

2) We would have to rewrite the Fundamental Theorem of Arithmetic (unique factorization of integers) to account for the special case of 1. After all, 6 = 3*2 = 3*2*1 = 3*2*1*1 and so on.

Answer 3

No... it is not a prime a number.
Because the definition of a prime number says that,
A number p greater than or equal to 2 is said to be a prime if it is divisible only by 1 and itself.
So, a prime number should have exactly two factors.
But 1 has only one factor.
Therefore, the number 1 is not prime.

Answer 4

No. The prime numbers exclude 1 by definition.

Answer 5

no

Answer 6

No.

Answer 7

no.