the factors are: 1,2,4,5,10,20. So Therefore there are 6 factors.
Prime numbers have only one rectangular array. Numbers with four factors have two types of rectangular array: 8 has 1 x 8 and 2 x 4. Numbers with six factors have three rectangular arrays: 20 has 20 x 1, 10 x 2, and 5 x 4.
