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Where 57421 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 57421 into a pocket calculator and turn it upside down: IZhLS — not quite a word, sorry.
- ➕ As a number, 57,421 = 7 × 13 × 631. Its digits add up to 19, a total 2,454 other ZIP codes share.
- 💾In binary, the way a computer stores it:
1110000001001101 - 🏠 Its numerical neighbours: 57420 (Akaska, SD, 113 mi away) and 57422 (Andover, SD, 23 mi away).
- 🔄 Backwards, 57421 becomes 12475 — and that is a real ZIP code: Ruby, NY, 1,213 miles away.
- 👥 63 other ZIP codes are made of exactly the same digits (12457, 12475, 12547, 12574, 12745, 12754, …). The farthest-flung twin is 12547 in Milton, NY, 1,223 miles away.
- 🧭 Farther north than 93% of all ZIP codes, and farther west than 77%.
- 🎯411 miles north of the geographic center of the Lower 48, near Lebanon, Kansas.
- 🌏 Dig straight through the Earth from 57421 and you would come out at 45.76°S, 82.09°E — 606 miles from Port-aux-Français, French Southern Territories, the nearest big city to that spot.
- ☀Longest day of the year: 15h 43m of daylight. Shortest: 8h 40m.
- 📏 At 33.3 square miles of land, 57421 is bigger than 48% of ZIP codes — room for about 25 Central Parks.
- Working out the sun…
- Checking the USGS…
Source: USGS.
People and housing
| Population | 75This ZIP75 |
|---|---|
| Households | 18This ZIP18 |
| Housing units | 26This ZIP26 |
| Median age | 16.6This ZIP16.6South Dakota38.0US 38.9 |
| Bachelor's degree or higher | 90.9%This ZIP90.9% |
| Population density | 2.2 / sq miThis ZIP2.2 / sq mi |
Land area
| Land area | 33.34 sq miThis ZIP33.34 sq mi |
|---|---|
| Water area | 0.09 sq miThis ZIP0.09 sq mi |
ZIP codes near 57421
| ZIP | City | Distance |
|---|---|---|
57432 | Claremont, SD | 7.8 mi |
57430 | Britton, SD | 10.6 mi |
57454 | Langford, SD | 12.2 mi |
57449 | Houghton, SD | 13.1 mi |
57446 | Hecla, SD | 14.3 mi |
57468 | Pierpont, SD | 19.7 mi |
58017 | Cogswell, ND | 20.1 mi |
57433 | Columbia, SD | 21.5 mi |
57247 | Lake City, SD | 21.6 mi |
57445 | Groton, SD | 22.4 mi |
Find every ZIP code within 10 miles of 57421 →
Questions about this ZIP code
Where is ZIP code 57421?
57421 is in Amherst, South Dakota, in Marshall County. Its published point location is 45.7555, -97.9071.
What county is 57421 in?
57421 lies in Marshall County.
What area code is 57421?
Amherst uses area code 605, from NANPA's telephone records.
What time zone is 57421 in?
57421 uses America/Chicago.
How many people live in 57421?
About 75 people live in ZIP code 57421, in 18 households, at 2.2 people per square mile. These are American Community Survey 5-year estimates for the ZIP Code Tabulation Area, not a headcount.
What ZIP codes are near 57421?
The closest are 57432 (7.8 mi), 57430 (10.6 mi), 57454 (12.2 mi), 57449 (13.1 mi) and 57446 (14.3 mi).
Is 57421 a PO Box ZIP code?
57421 is a standard ZIP code. A normal ZIP code with street delivery.
Download or cite
Cite this page
zipcodes.pro. “57421 ZIP Code — Amherst, South Dakota (Marshall County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/57421
Machine-readable version of these facts:
curl https://zipcodes.pro/zip/57421.jsonUnderlying data is public domain or openly licensed — sources, vintages and licences.