Two.
2 and p
Since p is prime it's only factor (other than one) is it's self.
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It has four factors: 1, 2, p, and 2p.
Here's the following proof that "product of two odd numbers is odd". Proof: Any odd number can be written in the form 2p+1. Let your first odd number be written in this form. Let your second odd number be written as 2q+1 - essentially the same form as above, but since p may not equal q, separate variables are used. Thus: First odd number x second odd number = (2p+1)(2q+1) = 2pq + 2p +2q +1. The plus one on the end indicates that the product is odd, as required.
Yes, it's always odd, and here's the proof: All odd numbers can be expressed as 2p + 1, where p is any integer. Multiply two of those together: (2n + 1)(2p + 1) = 4np + 2n + 2p + 1 = 2(np + n + p) + 1. Since both np, n, and p are integers, that means np + n + p is an integer; and since that integer is being multiplied by 2, it must be even. Thus, by adding 1 to that even number, the result will be odd.
Let p = any prime number. (2p -1) is called a Mersenne number. Any such number that is prime is called a Mersenne Prime. Father Mersenne wrote a list of numbers of this type which he thought were prime, but a few were not. In fact, most of the large Mersenne numbers are not prime, but all the really large numbers that have been proved to be prime are Mersenne Primes.
A prime number that is one more than a square number is known as a Sophie Germain prime. Sophie Germain primes are of the form 2p+1, where p is a prime number. For example, 17 is a Sophie Germain prime because it is one more than the square of 4, and both 4 and 17 are prime numbers. Sophie Germain primes have applications in number theory and cryptography.