Every ZIP code in the United States, with weather, radar, trivia and the numbers behind it. Five digits since 1963!

ZIP stands for Zone Improvement Plan. The codes went live on July 1, 1963.The lowest ZIP code is 00501 — the IRS in Holtsville, New York.The highest ZIP code is 99950, in Ketchikan, Alaska.Type 07734 into a calculator and turn it upside down: hELLO. It is Keansburg, New Jersey.12345 belongs to one company: General Electric in Schenectady, New York.The first digit is a region: 0 is New England and New Jersey, 9 is the West Coast, Alaska and Hawaii.Mr. ZIP, the cartoon mailman, was the mascot that sold the idea to America.ZIP+4 arrived in 1983 and can narrow a ZIP down to one side of one block.A ZIP code is a mail route, not a place: plenty of them cross county and even state lines.Play ZIP Hunt: guess the secret ZIP code of the day in six tries.
zipcodes.pro — ZIP/03821

03821

ZIP 03821 is in Dover, New Hampshire, in Strafford County; area code 603; Eastern time. Dover has 3 ZIP codes; the others are 03820 and 03822.

Type
No street area
Time zone
America/New_York
County
Strafford
Coordinates
43.1979, -70.8737

The Census map gives this ZIP code no delivery area of its own, which usually means it serves post office boxes, a single organization or a post office rather than streets of homes.

This ZIP code has no Census tabulation area of its own. Its point falls inside ZCTA 03820, whose figures describe that area — not this ZIP code.

☼ Live from 03821 — Dover, NH

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Where 03821 is

This ZIP code has no Census tabulation area, so there is no boundary to draw — the marker is its published point location.

★ Weird and wonderful facts about 03821
  • 🔢 Type 03821 into a pocket calculator and turn it upside down: IZBEO — not quite a word, sorry.
  • ➕ 03821 is a prime number. It cannot be divided by anything except 1 and itself. Its digits add up to 14, a total 1,416 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 111011101101
  • 🏠 Its numerical neighbours: 03820 (Dover, NH, 1 mi away) and 03822 (Dover, NH, 0 mi away).
  • 🔄 Backwards, 03821 becomes 12830, which is not a ZIP code at all.
  • 👥 70 other ZIP codes are made of exactly the same digits (01238, 01832, 02138, 02381, 02813, 02831, …). The farthest-flung twin is 83210 in Aberdeen, ID, 2,096 miles away.
  • 🧭 Farther north than 84% of all ZIP codes, and farther east than 96%.
  • 🎯1,445 miles east of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 03821 and you would come out at 43.20°S, 109.13°E — 859 miles from Perth, Australia, the nearest big city to that spot.
  • ☀Longest day of the year: 15h 23m of daylight. Shortest: 8h 59m.
🌙 The sky over 03821 today
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Source: USGS.

Business and tax activity

Business establishments19This ZIP19
Employees151This ZIP151
Annual payroll$8,066,000This ZIP$8,066,000

Land area

ZIP codes near 03821

ZIPCityDistance
03822 Dover, NH 0.0 mi
03820 Dover, NH 0.9 mi
03869 Rollinsford, NH 2.2 mi
03823 Madbury, NH 3.8 mi
03878 Somersworth, NH 3.9 mi
03824 Durham, NH 6.0 mi
03903 Eliot, ME 6.1 mi
03908 South Berwick, ME 6.5 mi
03901 Berwick, ME 7.2 mi
03839 Rochester, NH 7.5 mi

Find every ZIP code within 10 miles of 03821 →

Questions about this ZIP code

Where is ZIP code 03821?

03821 is in Dover, New Hampshire, in Strafford County, part of the Boston-Cambridge-Newton, MA-NH metropolitan area. Its published point location is 43.1979, -70.8737.

What county is 03821 in?

03821 lies in Strafford County.

What area code is 03821?

Dover uses area code 603, from NANPA's telephone records.

What time zone is 03821 in?

03821 uses America/New_York.

What ZIP codes are near 03821?

The closest are 03822 (0 mi), 03820 (0.9 mi), 03869 (2.2 mi), 03823 (3.8 mi) and 03878 (3.9 mi).

Is 03821 a PO Box ZIP code?

Possibly. The Census map gives this ZIP code no delivery area of its own, which usually means it serves post office boxes, a single organization or a post office rather than streets of homes.

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Cite this page

zipcodes.pro. “03821 ZIP Code — Dover, New Hampshire (Strafford County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/03821

Machine-readable version of these facts:

curl https://zipcodes.pro/zip/03821.json

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