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Where 78721 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.
- 🔢 Type 78721 into a pocket calculator and turn it upside down: IZLBL — not quite a word, sorry.
- ➕ 78721 is a prime number. It cannot be divided by anything except 1 and itself. Its digits add up to 25, a total 2,242 other ZIP codes share.
- 💾In binary, the way a computer stores it:
10011001110000001 - 🏠 Its numerical neighbours: 78720 (Austin, TX, 6 mi away) and 78722 (Austin, TX, 2 mi away).
- 🔄 Backwards, 78721 becomes 12787 — and that is a real ZIP code: White Sulphur Springs, NY, 1,497 miles away.
- 👥 20 other ZIP codes are made of exactly the same digits (12778, 12787, 17728, 17827, 17872, 21778, …). The farthest-flung twin is 12787 in White Sulphur Springs, NY, 1,497 miles away.
- 🧭 Farther south than 92% of all ZIP codes, and farther west than 76%.
- 🎯662 miles south of the geographic center of the Lower 48, near Lebanon, Kansas.
- 🌏 Dig straight through the Earth from 78721 and you would come out at 30.27°S, 82.32°E — 1,462 miles from Port-aux-Français, French Southern Territories, the nearest big city to that spot.
- ☀Longest day of the year: 14h 06m of daylight. Shortest: 10h 11m.
- 📏 At 3.6 square miles of land, 78721 is bigger than 16% of ZIP codes — room for about 2.7 Central Parks.
- Working out the sun…
- Checking the USGS…
Source: USGS.
People and housing
| Population | 10,997This ZIP10,997 |
|---|---|
| Households | 4,973This ZIP4,973 |
| Housing units | 5,341This ZIP5,341 |
| Median age | 33.8This ZIP33.8Texas35.6US 38.9 |
| Median household income | $84,573This ZIP$84,573Texas$78,476US $80,734 |
| Median home value | $523,000This ZIP$523,000Texas$283,800US $332,700 |
| Median gross rent | $1,482This ZIP$1,482Texas$1,403US $1,413 |
| Bachelor's degree or higher | 51.6%This ZIP51.6% |
| Mean commute | 22.8 minThis ZIP22.8 min |
| Population density | 3,082.1 / sq miThis ZIP3,082.1 / sq mi |
Business and tax activity
| Business establishments | 310This ZIP310 |
|---|---|
| Employees | 5,704This ZIP5,704 |
| Annual payroll | $572,568,000This ZIP$572,568,000 |
| Tax returns filed | 5,880This ZIP5,880 |
| Total adjusted gross income | $530,947,000This ZIP$530,947,000 |
Land area
| Land area | 3.57 sq miThis ZIP3.57 sq mi |
|---|---|
| Water area | 0.00 sq mi |
Other place names in 78721
Census places whose land this ZIP code overlaps. The Postal Service may accept other city names in an address, too.
ZIP codes near 78721
| ZIP | City | Distance |
|---|---|---|
78702 | Austin, TX | 1.9 mi |
78722 | Austin, TX | 2.3 mi |
78723 | Austin, TX | 2.3 mi |
78742 | Austin, TX | 2.5 mi |
78712 | Austin, TX | 3.1 mi |
78741 | Austin, TX | 3.4 mi |
78701 | Austin, TX | 3.5 mi |
78713 | Austin, TX | 3.6 mi |
78714 | Austin, TX | 3.6 mi |
78715 | Austin, TX | 3.6 mi |
Find every ZIP code within 10 miles of 78721 →
Questions about this ZIP code
Where is ZIP code 78721?
78721 is in Austin, Texas, in Travis County, part of the Austin-Round Rock-San Marcos, TX metropolitan area. Its published point location is 30.2713, -97.6835.
What county is 78721 in?
78721 lies in Travis County.
What area code is 78721?
Austin uses area codes 512 and 737, from NANPA's telephone records.
What time zone is 78721 in?
78721 uses America/Chicago.
How many people live in 78721?
About 10,997 people live in ZIP code 78721, in 4,973 households, at 3,082.1 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 78721?
$84,573 a year, against $78,476 across Texas.
What ZIP codes are near 78721?
The closest are 78702 (1.9 mi), 78722 (2.3 mi), 78723 (2.3 mi), 78742 (2.5 mi) and 78712 (3.1 mi).
Is 78721 a PO Box ZIP code?
78721 is a standard ZIP code. A normal ZIP code with street delivery.
Download or cite
Cite this page
zipcodes.pro. “78721 ZIP Code — Austin, Texas (Travis County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/78721
Machine-readable version of these facts:
curl https://zipcodes.pro/zip/78721.jsonUnderlying data is public domain or openly licensed — sources, vintages and licences.