Prime numbers that, when multiplied, equal another number are said to be the “prime factors” of that number. For example, 2 and 7 are the prime factors of the number 14.
Know MoreA prime number can only be multiplied by itself and the number 1. So, the number “8” is not prime because it’s possible to multiply “2” and “4” to produce the number 8. The number “7” is prime because no other whole numbers produce the number when multiplied together besides itself and the number 1. Determining prime factors of a number means breaking this number up into more numbers and then checking to see if those new numbers are prime. For example, the number “32” can be broken up into “8” and “4,” which when multiplied together make 32. But “8” and “4” aren’t prime numbers themselves. It’s necessary to break these numbers down further before they are prime factors. In this case, it takes four of the number “2” to make up the prime factors of number “32.” It’s also possible to write prime factors with an exponent if they include multiple of the same number. For example, the prime factors of 32 include “2” with an exponent of “4.”
Learn more about NumbersNine is not a prime number. It is a composite number, because it has more than two factors. A prime number is only divisible by one and by itself, and nine is divisible by one and by nine, but it is also divisible by the number three.
Full Answer >Fifteen is not a prime number. A prime number is a positive number that has only two possible divisors, 1 and itself. Fifteen can be divided by 3 and 5 as well as 1 and itself.
Full Answer >The number 49 is divisible by seven, so it is not a prime number. A prime number is a number that is only divisible by the number 1 and itself.
Full Answer >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 definition of a prime number.
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