Wholesale retailer Costco (NASDAQ: COST) announced a 13% increase to its dividend last week. The double-digit dividend increase was a good reminder why the stock has become a great investment for investors looking for income in their portfolio. The retailer has now increased its dividend 17 years in a row, and there's likely more growth to come in the years ahead. But there's much more to this dividend stock than its 0.9% dividend yield and years of consistent growth. Here's why dividend investors may want to take a closer look at Costco stock. Image source: Getty Images. Accelerated growth First of all, it's worth noting that Costco's recently announced dividend increase was a significant acceleration over the company's 8% dividend increase last year. The dividend's accelerated growth, however, isn't surprising given the company's strong underlying business momentum. Costco's trailing-12-month revenue rose 13% and its trailing-12-month earnings per share jumped 16%. Further, Costco's sales for the five-week period ending April 4 rose 16%, with its same-store sales rising 11% when excluding the impacts of changes in gasoline prices and foreign exchange rates. While the company's strength is in brick-and-mortar sales, management isn't overlooking the opportunity in e-commerce. E-commerce sales in Costco's most recently reported quarter were up 76% year over year. And even as the economy reopens and COVID-19 vaccines ramp up and more people are willing to venture out to stores, Costco still saw 55% growth in e-commerce sales for the five-week period ended April 4. Don't forget about Costco's special dividend But here's what investors giving a surface-level look at Costo stock as a potential dividend stock often miss: in the past, the company has -- from time to time -- paid out massive special dividends on top of its regular dividend payments. Late last year, for instance, Costco paid out a $10 special cash dividend. This was 14 times larger than its quarterly payment at the time. While Costco management never guarantees investors that it will pay out a special dividend, the massive payday for investors has been a somewhat regular occurrence for the company. Costco paid $7, $5, $7, and $10 special dividends in 2012, 2015, 2017, and 2020, respectively. With so many special dividends paid since 2012 -- and given their size relative to Costco's regular dividend -- it's safe to say that Costco's sub-1% dividend yield doesn't tell the whole story for this company's dividend payout potential. Even more, Costco investors should consider that the company's regular dividend accounts for less than 30% of the company's earnings. This means there's plenty of room for further growth in Costco's regular dividend -- especially since its earnings are trending sharply upward. Costco's strong business momentum, long history of dividend growth and special dividends, and low payout ratio make this a great dividend stock for investors looking for income. 10 stocks we like better than Costco WholesaleWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Costco Wholesale wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of February 24, 2021 Daniel Sparks owns shares of Costco Wholesale. His clients may own shares of Costco Wholesale. The Motley Fool owns shares of and recommends Costco Wholesale. The Motley Fool has a disclosure policy.Source