Is 381 composite or prime

Answer 1

To check

1. It is NOT an even number , so will not divide by '2'

2. It does NOT end in '5' , so will not divide by '5'.

3. The digits 381 do not sum to '9' ( 3+ 8 + 1= 12 = 3) So does not divide by '9'. 4. The clue is that the digits sum to '3' . Three is a Prime number , so it might divide by '3'. If so, then it is a composite number.

Hence

3)381 = 127 : No remainder.

So 127 X 3 = 381 / Hence it is a composite number.

NB When testing for composition of numbers, the other prime number to try is '7'.

Answer 2

Since the sum of the digits is divisible by 3, (3+8+1=12), the entire number is divisible by 3.

Since it has at least one factor other than 1 and itself, it's not prime.

Answer 3

composite