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zipcodes.pro — ZIP/21771

21771

ZIP 21771 is Mount Airy, Maryland, mostly in Frederick County; area codes 240, 301 and 227; Eastern time.

Type
Standard
Time zone
America/New_York
County
Frederick +3 more
Population
33,031
Coordinates
39.3949, -77.1582
☼ Live from 21771 — Mount Airy, MD

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Where 21771 is

Approximate ZIP boundary (Census ZCTA 2020). ZIP codes are mail routes, not areas, so the shape shown is the Census tabulation area that approximates it.

★ Weird and wonderful facts about 21771
  • 🔢 Type 21771 into a pocket calculator and turn it upside down: ILLIZ — not quite a word, sorry.
  • ➕ As a number, 21,771 = 3 × 3 × 41 × 59. Its digits add up to 18, a total 2,332 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 101010100001011
  • 🏠 Its numerical neighbours: 21770 (Monrovia, MD, 6 mi away) and 21773 (Myersville, MD, 23 mi away).
  • 🔄 Backwards, 21771 becomes 17712, which is not a ZIP code at all.
  • 👥 16 other ZIP codes are made of exactly the same digits (11727, 11772, 12177, 12771, 17127, 17217, …). The farthest-flung twin is 71172 in Bossier City, LA, 1,029 miles away.
  • 🧭 Farther north than 52% of all ZIP codes, and farther east than 81%.
  • 🎯1,138 miles east of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 21771 and you would come out at 39.39°S, 102.84°E — 892 miles from Perth, Australia, the nearest big city to that spot.
  • ☀Longest day of the year: 14h 57m of daylight. Shortest: 9h 23m.
  • 📏 At 89.5 square miles of land, 21771 is bigger than 75% of ZIP codes — room for about 68 Central Parks.
🌙 The sky over 21771 today
  • Working out the sun…
🌋 Shake report
  • Checking the USGS…

Source: USGS.

People and housing

Population33,031This ZIP33,031
Households11,226This ZIP11,226
Housing units11,758This ZIP11,758
Median age40.9This ZIP40.9Maryland39.4US 38.9
Median household income$157,302This ZIP$157,302Maryland$103,678US $80,734
Median home value$556,200This ZIP$556,200Maryland$419,900US $332,700
Median gross rent$2,252This ZIP$2,252Maryland$1,705US $1,413
Bachelor's degree or higher48.8%This ZIP48.8%
Mean commute36.1 minThis ZIP36.1 min
Population density369.0 / sq miThis ZIP369.0 / sq mi

Business and tax activity

Business establishments759This ZIP759
Employees7,538This ZIP7,538
Annual payroll$399,631,000This ZIP$399,631,000
Tax returns filed15,440This ZIP15,440
Total adjusted gross income$1,834,380,000This ZIP$1,834,380,000

Land area

Land area89.52 sq miThis ZIP89.52 sq mi
Water area0.18 sq miThis ZIP0.18 sq mi

Counties 21771 spans

A ZIP code is a mail route and ignores county lines. Shares are by overlapping land area.

CountyShare of this ZIP
Frederick County 51.4%
Carroll County 26.2%
Howard County 18.2%
Montgomery County 4.2%

Other place names in 21771

Census places whose land this ZIP code overlaps. The Postal Service may accept other city names in an address, too.

ZIP codes near 21771

ZIPCityDistance
21792 Unionville, MD 5.7 mi
21765 Lisbon, MD 6.1 mi
21770 Monrovia, MD 6.1 mi
21774 New Market, MD 6.3 mi
21797 Woodbine, MD 6.5 mi
20872 Damascus, MD 7.1 mi
21762 Libertytown, MD 7.6 mi
21776 New Windsor, MD 9.1 mi
21723 Cooksville, MD 9.5 mi
21754 Ijamsville, MD 9.5 mi

Find every ZIP code within 10 miles of 21771 →

Questions about this ZIP code

Where is ZIP code 21771?

21771 is in Mount Airy, Maryland, in Frederick County, part of the Washington-Arlington-Alexandria, DC-VA-MD-WV metropolitan area. Its published point location is 39.3949, -77.1582.

What county is 21771 in?

21771 spans 4 counties: Frederick County, Carroll County, Howard County and Montgomery County. Most of it falls in Frederick County, measured by overlapping land area — the county holding the most land in a ZIP code is not always the one holding the most residents.

What area code is 21771?

Mount Airy uses area codes 240, 301 and 227, from NANPA's telephone records.

What time zone is 21771 in?

21771 uses America/New_York.

How many people live in 21771?

About 33,031 people live in ZIP code 21771, in 11,226 households, at 369.0 people per square mile. These are American Community Survey 5-year estimates for the ZIP Code Tabulation Area, not a headcount.

What is the median household income in 21771?

$157,302 a year, against $103,678 across Maryland.

What ZIP codes are near 21771?

The closest are 21792 (5.7 mi), 21765 (6.1 mi), 21770 (6.1 mi), 21774 (6.3 mi) and 21797 (6.5 mi).

Is 21771 a PO Box ZIP code?

21771 is a standard ZIP code. A normal ZIP code with street delivery.

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Cite this page

zipcodes.pro. “21771 ZIP Code — Mount Airy, Maryland (Frederick County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/21771

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