That is the approximate number of weapons that were "placed" there before the Shah left. They were disabled, but not destroyed or removed right before the Shah fell.
At least one of them ended up in Saudi Arabia, when the new government flew a plane in to demonstrate to he Saudis that an air defense system run on connections rather than some merit is rather porous. The plane that flew in had well maintained engines (the French techs did a great job), but no avionics and no weapon system. Corroded to the rails was one of the tactical nuclear weapons, still disabled and non-functional.
It was disposed of along with the other garbage.
I would note that "weapons of mass destruction" are a fools game for most countries. Fuel oil bombs and short range missiles would have made Iraq a great deal more of a threat than its WMD programs. There is a reason the Nazis generated massive amounts of poison gases, yet only deployed them against civilians in concentration camps. In very specific situations (such as a small, heavily defended target, such as Israel) there may be no better choice (though see saturation missile attacks with missile launched fuel oil bombs) ...
For twenty billion dollars, if you spent eight billion on desalination plants and schools for Palestinians, five on producing LAWs (light anti-tank weapons) and five on fuel oil bombs, while running a student exchange program (the last two billion) you would get a lot further, and a lot more impact than Saddam ever did seeking WMDs.
Not to mention, but nuclear weapons rot. There is a reason radioactive decay is called "decay." And it happens faster when nuclear material is put together in weapons. The soviets had far more environmental damage from their remanufacturing program than they ever did building the weapons.
Just like men on the ground, nuclear weapons are subject to attrition and age. Just like men on the ground, it is often easy to overestimate what they mean.