Looks like its this song one by three dog night http://www.threedognight.com/l_one.html
When the smaller one is a factor of the larger one. (That also means the largerone is a multiple of the smaller one.) The smaller number is the GCF of both.
Every number multiplied by its reciprocal produce 1.
Any number and its inverse example 4 x 1/4=1 2x 1/2=1
1 x 1 that's it lol