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Proper Factors — Name the Number

A number’s proper factors are all its factors (or divisors) apart from the number itself. For instance, 12 has the proper factors 1, 2, 3, 4, and 6, while a prime such as 7 has just one, 1. Each list below gives every proper factor of a hidden number. Work backwards to name it.

ExampleThe numbers below are all the proper factors of one hidden number.
1, 2, 19
Work backwards: what is the hidden number? 38
  1. 1.The numbers below are all the proper factors of one hidden number.
    1, 2, 4
    Work backwards: what is the hidden number?
  2. 2.The numbers below are all the proper factors of one hidden number.
    1, 3, 5, 9, 15
    Work backwards: what is the hidden number?
  3. 3.The numbers below are all the proper factors of one hidden number.
    1, 5, 7
    Work backwards: what is the hidden number?
  4. 4.The numbers below are all the proper factors of one hidden number.
    1, 2, 4, 8, 16
    Work backwards: what is the hidden number?
  5. 5.The numbers below are all the proper factors of one hidden number.
    1, 2, 4, 5, 10
    Work backwards: what is the hidden number?
  6. 6.The numbers below are all the proper factors of one hidden number.
    1, 2, 23
    Work backwards: what is the hidden number?
  7. 7.The numbers below are all the proper factors of one hidden number.
    1, 3, 7
    Work backwards: what is the hidden number?
  8. 8.The numbers below are all the proper factors of one hidden number.
    1, 2, 4, 8
    Work backwards: what is the hidden number?
  9. 9.The numbers below are all the proper factors of one hidden number.
    1, 2, 3, 4, 6, 8, 12, 16, 24
    Work backwards: what is the hidden number?
  10. 10.The numbers below are all the proper factors of one hidden number.
    1, 2, 3, 6, 9
    Work backwards: what is the hidden number?
  11. 11.The numbers below are all the proper factors of one hidden number.
    1, 3, 9
    Work backwards: what is the hidden number?
  12. 12.The numbers below are all the proper factors of one hidden number.
    1, 2, 3, 4, 6, 9, 12, 18
    Work backwards: what is the hidden number?
  13. 13.The numbers below are all the proper factors of one hidden number.
    1, 2, 3, 6, 9, 18, 27
    Work backwards: what is the hidden number?
  14. 14.The numbers below are all the proper factors of one hidden number.
    1, 3, 5
    Work backwards: what is the hidden number?