Find the Missing NumberPro Problems > Math > Number and Quantity > Number Theory > Divisors
Find the Missing Number
What number is missing from the following list?
1, 2, 3, 4, 6, 8, 9, 18, 24, 36, 72
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x has 2n - 9 more divisors than x - 4, and it has 2n - 7 divisors more than x + 5.
What are the possible values of n, if x is a positive integer less than 50?
LCM and GCF
The least common multiple of x and 36 is 180. The greatest common factor of x and 36 is 4. What is the value of x?
I had enough donuts to share evenly among twelve people without splitting any donuts. Then someone stole sixteen donuts, leaving me with enough to share evenly among seven people. If instead of sharing among seven people, I shared the remaining donuts among four people, how many did each person get, assuming I started with fewer than 100 donuts?
Leaping up the Obelisk
An obelisk has no more than 100 stairs. If I go up the stairs two at a time, there will be one step left over at the top. If I go up the stairs three at a time, there will be two left at the top. If I go up the stairs seven at a time, there will be six stairs left over at the top. What is the maximum number of stairs the obelisk could have?
GCF and LCM
The greatest common factor of two positive integers is 12, and their least common multiple is 72. If the sum of the numbers is less than 72, what are the numbers?
Reduce the following number to its prime factorization, without use of a calculator: 1006005. Explain the steps in your process.
Two, Three, but not Six
How many integers between 1 and 100 inclusive are multiples of either 2 or 3, but not of 6?
Multiples of Two and Three
How many integers between 1 and 1000 inclusive are multiples of either 2 or 3?