What are the proper factors of the numbers from 1 to 100?

Answer 1

The proper factors of a number are all its factors except itself. Sometimes, the number 1 is also excluded. So, the proper factors of 6 are either 1, 2, and 3, or if excluding the number 1, they are 2 and 3. (If your instructor distinguishes between proper factors and proper divisors, then proper factors are all the factors of a number except 1 and itself, while proper divisors are all the factors of a number except itself, but often proper factors is the only term used, so check whether 1 is included in the definition you are using.)

The list of factors in the question "What are the factors of the numbers from 1 to 100" (see link below) includes both 1 and the number itself, but if you remove the number itself, and the 1 if it is excluded in the definition of proper factor that you are using, you will have the complete list of proper factors.

The prime numbers, which only have themselves and 1 as factors, are in bold in the list of factors on that page. Their proper factors are either the number 1, or if 1 is excluded, they have no proper factors.

Short List of Proper Factors:

As an example, here are the proper factors (including 1, which is sometimes used and sometimes not) for the first 10 numbers:

1: No proper factors

2: 1

3: 1

4: 1, 2

5: 1

6: 1, 2, 3

7: 1

8: 1, 2, 4

9: 1, 3

10: 1, 2, 5

A less unwieldy versionIn practice, it seems unlikely that anyone wants you to continue the above list to 100. (That would be 3 sides of handwritten A4 paper.) Maybe they only wanted to know which numbers appear in the list of proper factors. For example, the proper factors of numbers from 1 to 10 are 1, 2, 3, 4 and 5 (as you can see above).