整整 (zhěng zhěng) is an adverb placed before numbers or durations to emphasize that the amount is exactly and completely that number, often implying it's a large or surprising amount (e.g., 'a whole three years'). It differs from 整 (zhěng), an adjective meaning 'whole/entire' that cannot be used this way, and from 完全 (wán quán), which means 'completely' in the sense of thoroughness, not exact quantities.