1 + 5 + 6 + 3 = 15
15 is a multiple of 3.
15603 is a multiple of 3.
That makes it composite.
A prime number has only 2 factors which are 1 and itself. Composite numbers are everything else except 1 and 0. 1 and 0 are neither prime, nor composite.
It is a composite number because it has at least one positive factor other than one or itself.
There is no set formula to make a prime number into a composite but usually adding 1 will work. A prime number has only 2 factors which are 1 and itself. Composite numbers are everything else except 1, 2, and 0.
You could try dividing by composite numbers but the number that you are testing is divisible by a composite number, then it will be divisible by a prime factor of that composite number and that prime factor will be smaller. It is always easier to work with smaller numbers.
Composite Work: A prime number is only divisible by itself and one. 74 is divisible by 2 and 37 Not prime. As soon as you see that '4' at the end, you know it's an even number. No even number (except '2') can be a prime, because in addition to itself and '1', it also has '2' for a factor.
where is it
There is no work. The only prime number ending in 5 is 5.
33772 ends with a 2. Any positive integer ending with 0, 2, 4, 6 or 8 - other than 2 itself - is divisible by 2 and so is a composite number. The fact that it has one proper factor is sufficient to establish that it is not a prime. You do not even need to know its factors.
13 is already prime. Just write it down.
456
5 x 13 = 65 To show work, divide 65 by 5.
Work back from 999:999 is odd ... no.998 is even and divisible by 2, so it is composite. (All even numbers are composite!)Further Information:-All even numbers are composite except for 2 which is a prime number.