What makes a stock a good choice for a retirement investment? Stability is one of the most important things, but other important factors can include a strong dividend and the potential for steady long-term growth.

We asked three of our analysts to share their favorite retirement stocks, and here is what they had to say.

Dan Caplinger: Iron Mountain (NYSE:IRM) is a stock that many retirement investors have overlooked, but it has taken an innovative approach to the business of storage and information-management services that is paying off for its investors. Iron Mountain specializes in providing the facilities that companies need to store important business records, and given regulatory requirements to keep substantial volumes of documents, the company has a lot of potential to cater to rising demand from a wide variety of business clients.

Most importantly for retirement investors, though, Iron Mountain recently decided to convert into a real-estate investment trust. Because of that, Iron Mountain will have to pay out nearly all of its income in the form of dividends, and currently, the REIT's shares carry a yield above 5%. Although the company does most of its business in North America, Iron Mountain has also looked to expand around the world, making its services more attractive to multinationals that prefer one-stop service for all their global information-management needs. Would-be investors need to understand that with dividends tied to earnings, Iron Mountain's payments to shareholders could become more volatile than they've been in the past. Nevertheless, with the long-promised move toward electronic records management still having failed to eliminate the need for a physical paper trail in most industries, Iron Mountain should thrive for many years to come.

Matt Frankel: Realty Income (NYSE:O) is one of my favorite retirement stocks, and for a good reason. The company is an excellent combination of growth and income that works in any portfolio before and after retirement.

The company is a REIT that invests in commercial properties that are leased to retail tenants, which provides stable, growing income in two main ways. First, commercial leases are very long, and can stretch for 15 years or more with annual rent increases built right into the lease. So, once the company finds a tenant for a certain property, they don't have to worry about it again for a long time.

Second, retail tenants are on a "net lease," which means that the tenants are responsible for property taxes, insurance, and building maintenance, thereby taking these fluctuating costs out of the equation for investors. This leads to predictable, growing income that simply cannot be matched anywhere else.

Currently, Realty Income pays a dividend yield of about 4.8% on a monthly basis, and has raised its dividend an impressive 77 times since going public in 1994 -- an average of nearly four times per year. Investors have enjoyed a total return of 16.4% per year over the past two decades, handily beating the S&P's 9.5% average return.

Realty Income is an extremely attractive retirement stock, simply because it's tough to match this fantastic combination of growth and income anywhere else.

Selena Maranjian: There's a lot to like about Boeing (NYSE:BA) beyond its solid dividend -- which was just hiked by 25% and recently yielded 2.9%. (Over the past decade, it has risen by an annual average of 14%, and with a payout ratio near 52%, it has plenty of room for further increases.) The company has also upped its share repurchase authorization to $12 billion and has already spent $6 billion on that, with the share count falling from 768 million at the end of 2013 to a fitting 747 million recently. Boeing has been a long-term rewarder of shareholders, with its share price growth averaging more than 11% annually over the past 10 and 30 years alike.

The company's future seems rosy, too. As long as we have air travel, fleets of aircraft will have to be rejuvenated with new planes. Indeed, Boeing's backorder is a whopping $490 billion. As my colleague Daniel Miller has pointed out, that's nearly five times the company's expected 2014 revenue. In 2014 alone, it has received orders for roughly 1,400 planes -- outpacing its rival Airbus (NASDAQOTH:EADSY). Meanwhile, some are suggesting that Boeing and Airbus might work together on fighter jets to strengthen their position in that market and draw more military dollars.

Retirees like reliability, and Boeing certainly seems assured of plenty of demand. The company is speeding up its production rate, and its long-beleaguered 787 Dreamliner is finally nearing profitability. While its revenue has grown by about 5.6% annually over the past decade, earnings have grown by 20.4%, reflecting successful cost-cutting and share reduction. Boeing's stock looks attractively valued, as well, with its recent and forward-looking P/E ratios of 18 and 14.6 below its five-year average of 19.

the_motley_fool has no position in any stocks mentioned. Dan Caplinger has no position in any stocks mentioned. Matthew Frankel owns shares of Realty Income. Selena Maranjian has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.