Yes, you put a hyphen between seventy and two: seventy-two. Does seventy two need a hyphen? As 72 is a compound number in between 21 and 99 it needs a hyphen; therefore writing 72 in full is seventy-two. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.