500
The number of parts the entire seder has and their Hebrew names (at least three must be mentioned).
What are fifteen parts: Kaddesh, Urechatz, Karpas, Yachatz, Maggid, Rachtzah, Motzi, Matzah, Maror, Korekh, Shulchan Orekh, Tzafun, Barekh, Hallel, and Nirtzah