For people like me who didn't know what a "2-adic eval" is, it's a fancy way of saying that 52![1] can be divided by two 49 times and still give an integer.

If you factor the number 52! (https://wolframalpha.com/input?i=factor+52%21), you can see the term 2^49. If you divide 52! by two 49 times, you are still left with an integer.

[1]: 52 factorial, 52*51*50*...*2*1, the number of different orderings of the 52 cards in a standard deck