When you convert the number into its prime factors

16000 = 2^8 x 5^4

Now as per a rule to find number of factors is in the following thread:

http://www.gmatclub.com/phpbb/viewtopic ... ht=#241853
In general to find the number of divisors you find the total number of factors of each term (don't forget 1) ....

In this case for 2^8 the factors are : 1, 2, 4, 8, ... 2^8

which is 9 (1+8)

For 5, the total number of factors are : 1,5, ... 5^4 which is a total of 5 (1+4)

Therefore total factors = 9 x 5 = 45.

Note that in the thread I linked you can extend the same notion to find the sum of all factors...

Yurik79 wrote:

Haas please explain this part

# of factors of 16000 = (1+8)x(1+5) = 45 I don't understand it.Thanks in advance