*Are there any two primes that are NOT a factor of $ M$ that multiply up to $ M$ ?*

**Fact:** Any two primes that multiply up to $ M$ . Must be factors of $ M$ !

Thus because of the fact above an $ O(1)$ algorithm exists. It always outputs $ NO$

## Complement

*Are there any two primes that are a factor of $ M$ that multiply up to $ M$ ?*

**Fact:** A complement of a decision problem does not always require to always return $ YES$ or $ NO$ . It can be either one!

(eg. $ M$ = 6 and two primes that multiply up to $ M$ are $ 3$ ,$ 2$ .)

Well, this I find interesting this is deciding $ Semi-Primes$ .

## Question

Shouldn’t $ Semi-Primes$ be in $ P$ , because what was shown above?