There are 6 factor pairs of 819:
As a product of its prime factors: 3*3*7*13 = 819
819 273,3 91,3,3 13,7,3,3
Sixteen factor pairs.
2 factor pairs
There are 3 factor pairs of 16.
Three factor pairs
30 has four factor pairs:30,115,210,36,5
225 has five factor pairs:225,175,345,525,915,15
20 has 3 factor pairs. Pairs are (1,20), (2,10) and (9,9)
12 has 3 factor pairs and the pairs are (1,12), (2,6) and (3,4).
76 has 3 factor pairs: (1,76), (2,38), (4,19).
"Dose" is a measured portion of a medicine. I am not aware of any factor pairs related to dose 18 or any other measured quantities of medication!18 does have 3 factor pairs.