Question

is 123456789 a composite number​

Answer 1

COMPOSITE NUMBER

What is a composite number?

→ A  number which has more than two factors (1 and the no. itself) is known as a composite number.

Eg. :- 6 = 1,2,3,6

        10 = 1,2,5,10

        21 = 1,3,7,21

In the above examples, we can see that the numbers have factors other than 1 and the no. itself, therefore they are composite numbers.

Now, back to the question.

Let us try hit and trial method and start dividing the number with smaller numbers.

Since, it is an odd number therefore, it cannot be divided by 2.

Let's try it out by 3:-

123456789/3 = 41152263

Another way to check if a no. is divisible by 3 is that, if the sum of all the digits of a number is a multiple of 3 then it will be divisible by 3.

1+2+3+4+5+6+7+8+9 = 45 which is divisible by 3. This means that 123456789 will also be divisible by 3.

We can see that, the given number is divided by other than 1 and 123456789 itself.

The other factor is 3 .

We do not need to calculate further and check its other factors as it is now proven that 123456789 is a composite number.