Factoring the Number 31: A Simple Prime Exploration

Prime Number Identification with Factor Testing

Write all the factors of the following number: 31 31

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find all prime factors of the number
00:06 Let's try to divide
00:13 It seems the number itself is prime
00:23 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Write all the factors of the following number: 31 31

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Recognize that we need to find all factors of the number 31.
  • Step 2: Check for divisibility by integers up to the square root of 31.
  • Step 3: Conclude based on divisibility results.

Now, let's work through each step:

Step 1: We are given the number 31 31 .

Step 2: Check if 31 is divisible by integers less than or equal to the square root of 31. Since 315.57 \sqrt{31} \approx 5.57 , we need to test divisibility by 2, 3, 4, and 5:

  • 31÷2 31 \div 2 = 15.5 (not an integer, 31 is not divisible by 2).
  • 31÷3 31 \div 3 = 10.3333... (not an integer, 31 is not divisible by 3).
  • 31÷4 31 \div 4 = 7.75 (not an integer, 31 is not divisible by 4).
  • 31÷5 31 \div 5 = 6.2 (not an integer, 31 is not divisible by 5).

Step 3: Since 31 is not divisible by any integer other than 1 and 31, it is a prime number.

The factors of 31 are, therefore, 1 and 31, which are the only divisors possible.

Since the problem states "No prime factors" as a potential answer, this refers to the understanding that prime numbers aren't typically prime factored beyond recognizing them as such.

Therefore, the solution to the problem is:

No prime factors

3

Final Answer

No prime factors

Key Points to Remember

Essential concepts to master this topic
  • Rule: Prime numbers have exactly two factors: 1 and themselves
  • Technique: Test divisibility up to √31 ≈ 5.6, so check 2, 3, 4, 5
  • Check: Since 31 ÷ 2, 3, 4, 5 are all non-integers, 31 is prime ✓

Common Mistakes

Avoid these frequent errors
  • Confusing factors with prime factorization
    Don't think 'No prime factors' means 31 has no factors at all = wrong understanding! This means 31 cannot be broken down into smaller prime factors. Always remember that prime numbers like 31 have factors 1 and themselves, but no prime factorization.

Practice Quiz

Test your knowledge with interactive questions

Write all the factors of the following number: \( 9 \)

FAQ

Everything you need to know about this question

What does 'No prime factors' actually mean?

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It means 31 cannot be factored into smaller primes. The number 31 itself is prime, so it doesn't break down further. It's like saying '31 is already as simple as it gets!'

Why do I only need to test up to the square root?

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If a number has a factor larger than its square root, it must also have a corresponding smaller factor. Since we already checked all smaller factors, we don't need to go higher!

Don't all numbers have 1 and themselves as factors?

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Yes! But prime numbers have exactly these two factors and no others. Composite numbers have additional factors in between.

How is this different from finding prime factorization?

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Finding all factors lists every number that divides evenly (1, 31). Prime factorization breaks a number into prime building blocks. Since 31 is already prime, it has no prime factorization!

What if I missed checking a number?

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As long as you checked all integers from 2 up to 31 \sqrt{31} , you're good! For 31, that means checking 2, 3, 4, and 5 is sufficient.

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