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/20101

20101

ZIP 20101 is in Dulles, Virginia, in Loudoun County; area codes 703 and 571; Eastern time. Dulles has 5 ZIP codes; the others are 20102, 20103, 20104 and 20189.

Type
No street area
Time zone
America/New_York
County
Loudoun
Coordinates
39.0021, -77.4421

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 20166, whose figures describe that area — not this ZIP code.

☼ Live from 20101 — Dulles, VA

Weather right now

Asking the National Weather Service…

NEXRAD radar
Finding the nearest radar…
Local time: —

Where 20101 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 20101
  • 🔢 Type 20101 into a pocket calculator and turn it upside down: IOIOZ — not quite a word, sorry.
  • ➕ 20101 is a prime number. It cannot be divided by anything except 1 and itself. Its digits add up to 4, a total 27 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 100111010000101
  • 🏠 Its numerical neighbours: 20091 (Washington, DC, 24 mi away) and 20102 (Dulles, VA, 12 mi away).
  • 🔄 Backwards, 20101 becomes 10102 — and that is a real ZIP code: New York, NY, 221 miles away.
  • 👥 16 other ZIP codes are made of exactly the same digits (01012, 01021, 01102, 01201, 02110, 10012, …). The farthest-flung twin is 02110 in Boston, MA, 407 miles away.
  • 🧭 Farther south than 50% of all ZIP codes, and farther east than 80%.
  • 🎯1,127 miles east of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 20101 and you would come out at 39.00°S, 102.56°E — 892 miles from Perth, Australia, the nearest big city to that spot.
  • ☀Longest day of the year: 14h 54m of daylight. Shortest: 9h 25m.
🌙 The sky over 20101 today
  • Working out the sun…
🌋 Shake report
  • Checking the USGS…

Source: USGS.

Business and tax activity

Business establishments5This ZIP5
Employees15This ZIP15
Annual payroll$940,000This ZIP$940,000

Land area

ZIP codes near 20101

ZIPCityDistance
20189 Dulles, VA 0.5 mi
20103 Dulles, VA 0.6 mi
20163 Sterling, VA 0.8 mi
20167 Sterling, VA 0.8 mi
20598 Dhs, VA 0.9 mi
20164 Sterling, VA 2.5 mi
20166 Sterling, VA 2.5 mi
20147 Ashburn, VA 3.4 mi
20170 Herndon, VA 3.7 mi
20172 Herndon, VA 3.8 mi

Find every ZIP code within 10 miles of 20101 →

Questions about this ZIP code

Where is ZIP code 20101?

20101 is in Dulles, Virginia, in Loudoun County, part of the Washington-Arlington-Alexandria, DC-VA-MD-WV metropolitan area. Its published point location is 39.0021, -77.4421.

What county is 20101 in?

20101 lies in Loudoun County.

What area code is 20101?

Dulles uses area codes 703 and 571, from NANPA's telephone records.

What time zone is 20101 in?

20101 uses America/New_York.

What ZIP codes are near 20101?

The closest are 20189 (0.5 mi), 20103 (0.6 mi), 20163 (0.8 mi), 20167 (0.8 mi) and 20598 (0.9 mi).

Is 20101 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.

Download or cite

Cite this page

zipcodes.pro. “20101 ZIP Code — Dulles, Virginia (Loudoun County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/20101

Machine-readable version of these facts:

curl https://zipcodes.pro/zip/20101.json

Underlying data is public domain or openly licensed — sources, vintages and licences.