TITLE: Is every even number a value of the Carmichael function?
QUESTION [6 upvotes]: Except for the 1, all other values of the Carmichael function $\lambda$ are even. Does $\lambda$ take all even numbers? Is there an infinite family of even numbers that are not values of $\lambda$ ?
This question arose in the comments to What is the inverse of the Carmichael-function?.

REPLY [2 votes]: Also note that the list of even value not taken by $\lambda$ or $\phi$ is infinite. In fact, it can be shown that most even numbers are not in the image of either $\lambda$ or $\phi$.