To determine if 840 is a prime number or a composite number, we simply look at the factors for 840.
If the factors of 840 are only 840 and 1, then we know that 840 is a prime number. Otherwise, 840 is a composite number.
To explain better, if 840 is only divisible by 1 and 840, then it is a prime number, and if 840 is divisible by more than 840 and 1, then it is a composite number.
The factors of 840 are as follows:
1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 15, 20, 21, 24, 28, 30, 35, 40, 42, 56, 60, 70, 84, 105, 120, 140, 168, 210, 280, 420, 840
Therefore, since 840 is divisible by more than one and itself, the answer to the
question "Is 840 prime or composite?" is highlighted in blue below.
composite
Is 841 prime or composite?
OK. Now you know that 840 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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