Small point to make: the formula that people are using will help us determine the total number of POSITIVE divisors (factors).
It's worth noting that -1, -2, -3, -6 etc are also factors of (2²)(3³)(5³)(7), in which case the answer is actually 192 (96 positive factors and 96 negative factors)
From the Official Guide:
If x and y are integers and x ≠ 0, then x is a divisor (factor) of y provided that y = xn for some integer n. In this case, y is also said to be divisible by x or to be a multiple of x.
For example, 7 is a divisor or factor of 28 since 28 = (7)(4), but 8 is not a divisor of 28 since there is no integer n such that 28 = 8n.Given that the factors of a given integer can include negative integers, the GMAT test-makers restrict the discussion to POSITIVE integers, as in "If n =(2²)(3³)(5³)(7), then how many POSITIVE factors of n are there?"
Cheers,
Brent