Dividend stocks can be great sources of income for investors, but that doesn't mean they're risk free. Dividend payments are never guaranteed, and if a company runs into trouble, it could end up reducing or stopping its payouts completely.

That's why investors should always take a hard look at dividend stocks to make sure they have stable, long-term futures. The three stocks listed below are good bets to continue paying dividends for the long term and could be ideal for buy-and-hold investors who don't want to worry about checking on their portfolios every day.

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1. Walmart

Walmart (NYSE:WMT) is arguably one of the safest long-term investments available. The company dominates retail, and even rising competition from online retailer Amazon hasn't been enough to worry investors.

In its most recent earnings report, Walmart continued to show why it's still a great stock. The company beat expectations soundly, posting earnings per share of $1.16 versus the $1.09 analysts were looking for. Same-store sales of 3.2% also continue to be strong and were better than expectations of 3.1%. And despite concerns about a slowing economy, CEO Doug McMillon stated that the company is "prepared for a good holiday season." If he's right and the company has a strong Q4, the stock could be headed for some big gains in 2020.

Year to date, Walmart's shares have risen more than 28%. The stock also pays a dividend of 1.8%. This Dividend Aristocrat has increased its payouts for more than four decades, and there's little reason to expect that pattern will change anytime soon. While the increases have been modest, with the most recent hike being a 1.9% increase from $0.52 to $0.53, it will at least help in offsetting the impact of inflation over the years if that rate of increase continues.

2. Accenture

Accenture (NYSE:ACN) is another company that looks to have a solid future. With technological innovation gaining momentum and companies potentially facing some tougher economic times, a seasoned consulting company like Accenture can add a lot of value to many businesses.

The company recently announced that it would be working with SAP to develop cloud-based solutions that will help a variety of companies with their day-to-day operations. Called SAP Cloud for Utilities, the solution could improve automate sales processes and improve other business functions.

That's just one example of the type of value Accenture can add for its clients. As companies look to get leaner and maximize their profits, automation and finding ways to reduce costs will become more important than ever. That's why Accenture's services will be in demand for a long time, making its business very stable and secure over the long term.

Currently, the stock pays investors a dividend of around 1.6%. It has recently moved from semiannual payments to quarterly payouts. While not an Aristocrat itself, it has been raising its dividend payments for several years.

3.Pfizer

Pfizer (NYSE:PFE) might look a lot different in the future now that it is merging with pharmaceutical company Mylan. One of the concerns about Pfizer has been that its business might be too skewed toward legacy drugs that might not offer much in the way of long-term growth. Combining with the specialty drugmaker will allow Pfizer to have newer and more innovative products in its portfolio and shift its focus away from older ones.

While there may be some uncertainty as to how well the combined business will do, it's hard to imagine that the two profitable companies won't be stronger together. Mylan earned a modest $352.5 million last year (which pales in comparison to the $11.2 billion Pfizer generated in 2018), but what's important is that both businesses look strong overall.

Although the smaller Mylan doesn't pay its investors a dividend, Pfizer offers a generous yield of 3.7%. Pfizer has paid a dividend for decades and has increased its payouts in recent years, and it's unlikely to stop doing so after the two companies join forces.

Which stock is best?

Any one of the three stocks listed here could be a safe investment for many years. Pfizer might be more of a question mark in the short term, but for growth investors, it could have the most potential upside as a result of the business combination. Walmart, meanwhile, might be the most stable buy based on its sheer size and the leadership position it has in its industry. For extremely risk-averse investors who want to minimize their exposure to retail, Accenture might offer the best balance.