Gerunds can be used in two different ways. Sometimes, they are used exactly like nouns: they can be preceded by "the" and followed by "of", and they are modified by adjectives. Sometimes, they are more verb-like - they can take direct objects and be modified by adverbs.
In your sentence, the gerund is noun-like, because of the following "of": so it's the feature prevents [the] accidental dialing of numbers.
You could change the sentence to make the gerund more verb-like: The feature stops people accidentally dialing numbers.