I need the idler pulley number for the scotts1642h, the mower deck.

Hi,
Well, at least you gave the brand and model, though there are 3 idlers. Picture attached. Part numbers are:
14 #AM121108
32 #AM130307
39 #GY00054
Peace,
Clarke
PS I can email you the owners manual if you want it. Too large to post here as it is a few Mb.