How do you notice that it is factors or prime or composite numbers?

Answer 1

First of all, every number is a factor - of its multiples.

There is no general way to distinguish between prime and composite numbers. At one level, though, there are some simple ways. If the number is not 2, but ends in 0, 2, 4, 6 or 8 then it is a composite, If the number is not 5 but ends in 0 or 5 it is composite. If the number is not 3 but the sum of all the digits of a number is 3 or divisible by 3, then it is composite. There are moderately complicated divisibility rules for 7 and 11. But this method does not identify all composite numbers and there is no guaranteed method.

Answer 2

You can notice a number to be prime or composite by doing its factors. If it has more than 2 factors then it is a composite one.