5 of them.
76 has 3 factor pairs: (1,76), (2,38), (4,19).
One pair: it's a prime number.
Three of them.
An infinite number of times. If you restrict yourself to whole numbers, 500 has 6 factor pairs.
The factor pairs of 21 are:1, 213, 7Therefore, the number 21 has two pairs of positive integer factors.
Two:15,15,3
Two pairs: 1 and 26 2 and 13
Eight has two factor pairs. Including their negative counterparts, that makes four pairs.
Sixteen factor pairs.
The answer depends on the number of tiles.
The number 4 has two factor pairs. 1 x 4 and 2 x 2
49 of them.