Sixty-three is not a prime number. Sixty-three is classified as a composite number because it has divisors, and can be composed of other numbers than number one. More »

A prime number is a whole number greater than one that is only divisible by one or itself without leaving a remainder. A composite number is a whole number greater than one that is evenly divisible by more than one and i... More »

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The number one is neither prime nor composite. Prime numbers are positive integers greater than one that are evenly divisible only by themselves and one. Composite numbers are positive integers that have divisors other t... More »

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The number 51 is not a prime number; it is a composite number. A prime number is any positive number that can be divided evenly only by the number 1 and itself. More »

The number 21 is not a prime number. Prime numbers are numbers greater than one that are evenly divisible by only 1 and themselves. As the number 21 has multiple factors, including 1, 21, 3 and 7, it does not meet the de... More »

The number 19 is the eighth prime number. A prime number is a positive, whole number that is only divisible by one and itself. Nineteen is also the seventh Mersenne prime exponent, which is a prime number that is one les... More »

Eighty-nine is a prime number. To check for a prime number, divide it by every number from two to one less than the number (88 in this case). If no smaller number can be evenly divided into the number, which is the case ... More »

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