Pahrump, Nevada, is a hot retirement destination. Really hot.

The first reason why is obvious. No, it’s not because Pahrump is home to some of the country’s most famous legal brothels. It's because its average high temperature soars to 100 degrees each July. The all-time record for this isolated community west of Las Vegas is a sizzling 115 degrees.

The second reason has to do with a different set of numbers: the demographic definition of heat. Pahrump’s population of senior citizens is substantial and rapidly growing, earning first place in a new Portfolio.com/bizjournals study of America’s hottest retirement destinations.

Portfolio.com/bizjournals analyzed 940 metropolitan and micropolitan areas, searching for the most popular markets for people 65 or older. Each area was analyzed in four statistical categories, based on U.S. Census Bureau data. (To take a tour through the top retirement destinations, click here. To see the full analysis, click here.)

Retirees from the Pacific Northwest, the Midwest, and nearby California are drawn to Pahrump, a micropolitan area with 44,375 residents. Its warm, dry climate and its relative proximity to Las Vegas, slightly more than an hour’s drive away, are clear draws.

Pahrump ranks first on Portfolio.com/bizjournals’ retirement scale because of impressive performances in all of the study’s categories:

— Nearly 23 percent of its residents are 65 or older, a concentration that beats 920 of the other 939 markets. Seniors, in contrast, account for 12.5 percent of the nation’s population.

— The elderly outnumber the young in Pahrump, which has 103.7 senior citizens for every 100 kids and teens. That runs counter to the national rate of just 45.8 seniors per 100 youngsters.

— Pahrump’s population in the 65-plus age group skyrocketed by 69 percent between 2000 and 2008. That’s six times faster than the U.S. growth rate of 11.6 percent for the same cohort.

— The number of seniors in Pahrump is expanding more rapidly than the rest of its population. Portfolio.com/bizjournals devised a 100-point index to compare the two groups. Pahrump’s score of 131.09 means that its 65-plus growth rate is much faster than the corresponding rate for people under 65. The national index is 103.14.

Pahrump is the only area to register one of the 25 highest scores in each of these four categories, cementing its status as America’s hottest retirement destination.

Second place goes to Crossville, a micropolitan area on the Cumberland Plateau in eastern Middle Tennessee. Third place belongs to Oak Harbor, located on Whidbey Island off the mainland of Washington state.

Rounding out the top five are No. 4 Naples-Marco Island, Florida, and No. 5 Brevard, North Carolina.

Portfolio.com/bizjournals’ study contradicts several stereotypes about today’s retirees.

Senior citizens, for example, are not all drawn to Florida and the Southwest, the traditional havens. South Carolina placed as many markets in the study’s top 20 as Florida did: three apiece. Oregon and Washington both landed two slots in that elite group, the same number as Arizona.

Nor are retirees necessarily flocking to urban centers such as Miami, Phoenix, and Tampa. The largest market among the 40 hottest destinations is Ocala, Florida, with a metropolitan population of 329,600. The top-rated metro with at least 1 million residents is No. 135 Tucson.

Other locations have been growing in popularity, according to the study, including the Atlantic and Pacific coasts and the Great Lakes region. And some retirees are more interested in a specific type of community, such as a mountain town, than the state in which it’s located.