12 = 3 * 4
56 = 7 * 8
My username comes from The Penguin Dictionary of Curious and Interesting Numbers, where 39 is described as the first number with no particularly interesting properties.
I felt sorry for it.
My favourite:
Between any two rational numbers is an irrational number.
Between any two irrational numbers is a rational number.
But there are infinitely more irrational numbers!