To determine if 1991 is a prime number or a composite number, we simply look at the factors for 1991.
If the factors of 1991 are only 1991 and 1, then we know that 1991 is a prime number. Otherwise, 1991 is a composite number.
To explain better, if 1991 is only divisible by 1 and 1991, then it is a prime number, and if 1991 is divisible by more than 1991 and 1, then it is a composite number.
The factors of 1991 are as follows:
1, 11, 181, 1991
Therefore, since 1991 is divisible by more than one and itself, the answer to the
question "Is 1991 prime or composite?" is highlighted in blue below.
composite
Is 1992 prime or composite?
OK. Now you know that 1991 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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