Eight of them.
Two of them.
Three of them.
225 has five factor pairs:225,175,345,525,915,15
12 has three factor pairs, six if you count their negative counterparts.
The factor pairs of 91 are (1,91) and (7,13).
Sixteen factor pairs.
30 has four factor pairs:30,115,210,36,5
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.
The factor pairs of 21 are:1, 213, 7Therefore, the number 21 has two pairs of positive integer factors.
Eight of them.
Two of them.
Two.
One.