# How do you determine the prime factors of a number?

All composite numbers can be expressed as unique products of
prime numbers. This is accomplished by dividing the original number
and its factors by prime numbers until all the factors are prime. A
factor tree can help you visualize this.

Example: 210

210 Divide by two.

105,2 Divide by three.

35,3,2 Divide by five.

7,5,3,2 Stop. All the factors are prime.

2 x 3 x 5 x 7 = 210

That's the prime factorization of 210.

### Do you need to know all the factors of a number in order to determine if it is a prime or composite?

### How do you determine if a number is prime or composite?

If the number is divisible by any number and the quotient comes out to a whole number, then that number is composite. The number is prime when divided by a number, the answer is a decimal, then the number is prime. A prime number has exactly two factors, 1 and the number itself. Any number having more factors is a composite number.

### What is the LCM of 21 and 28?

To determine the least common multiple of two numbers, determine the prime factors of both number. Then, determine the prime factors they have in common. Multiply all their prime factors together (in other words, multiply both numbers together) and divide by the prime factors they have in common (in other words, their greatest common factor). The prime factors of 21 are 3 and 7. The prime factors of 28 are 2, 2, and 7. The…

### Do you need to know all of the factors of a number in order to determine if it is a prime or composite?

Yes, you do. And know them well, or else you'll get it wrong! Well, not exactly. To determine that a number is prime you need to know that the number has exactly two factors, which means that there are no other factors. You know that a number is composite by finding just one factor that is neither one nor the number itself.

### Can you Compare the number of factors of a prime number to the number of factors of a square number?

### What is least common multiple of 14 and 40?

To determine the least common multiple of two numbers, determine the prime factors of both number. Then, determine the prime factors they have in common. Multiply all their prime factors together and then divide by the prime factors they have in common. The prime factors of 14 are 2 and 7. The prime factors of 40 are 2, 2, 2, and 5. The common prime factors are a single 2. Therefore, the least common multiple…

### Why is 67 a prime number?

Look at the definition of a prime number. A prime number has no factors, other than 1, or itself. Look at the definition of a prime number. A prime number has no factors, other than 1, or itself. Look at the definition of a prime number. A prime number has no factors, other than 1, or itself. Look at the definition of a prime number. A prime number has no factors, other than 1, or…