GMAT Practice Question: How many positive integer divisors does 8 ! have?
Question
How many positive integer divisors does 8 ! have?
- 14
- 15
- 24
- 56
- 96
Topics: factorials, prime factorization, divisibility
Solution
Step 1
We prime factorize 8! by expressing each integer factor from 1 to 8 in its prime form
8! = 8 7 6 5 4 3 2 1
Step 2
We combine like prime factors by summing their exponents
8! = (2^3) 7 (2 3) 5 (2^2) 3 2 1 = 2^7 3^2 5^1 7^1
Step 3
We count the number of positive divisors by adding one to each exponent and multiplying
(7+1) (2+1) (1+1) (1+1) = 8 3 2 2 = 96
Answer
E
