To determine if 400 is a prime number or a composite number, we simply look at the factors for 400.
If the factors of 400 are only 400 and 1, then we know that 400 is a prime number. Otherwise, 400 is a composite number.
To explain better, if 400 is only divisible by 1 and 400, then it is a prime number, and if 400 is divisible by more than 400 and 1, then it is a composite number.
The factors of 400 are as follows:
1, 2, 4, 5, 8, 10, 16, 20, 25, 40, 50, 80, 100, 200, 400
Therefore, since 400 is divisible by more than one and itself, the answer to the
question "Is 400 prime or composite?" is highlighted in blue below.
composite
Is 401 prime or composite?
OK. Now you know that 400 is a composite number. Use our logic above and see if
you can figure out if the next number on our list is prime or composite before you check your answer.
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