About NumberWiki
NumberWiki is a reference site for integers. Every notable number gets a permanent, citable page that gathers its mathematical properties, sequence memberships, cultural significance, historical numeral renderings, and — when the number has a real-world meaning (an HTTP status, a port, a year, an IPv4 address) — explanatory context for that meaning too.
The goal is the answer to "what is interesting about this number?" — assembled once, kept fresh, and presented as a stable URL you can link to or cite.
What's on a number page
Every page is built from a layered classification pipeline. The layers are:
- Mathematical properties — parity, digit sum, digital root, bit width, palindrome status, reversed and rotated forms, square and cube roots, integer factorizations, divisor count, sum of divisors (σ), aliquot sum, factor pairs, and first multiples. All computed at request time from the integer itself; nothing is stored in the database except the page identity.
- Primality and factorization — primality is tested with deterministic Miller-Rabin (correct for all 64-bit integers), then trial division up to a large bound for the factorization. The primality test returns a definitive yes/no for any long.
- Sequence membership — Fibonacci, Lucas, Catalan, factorial, perfect, Mersenne, triangular, square, cube, pentagonal, hexagonal, heptagonal, octagonal, tetrahedral, square-pyramidal, Carmichael, harshad, kaprekar, narcissistic, strobogrammatic, palindrome, pronic, repdigit, repunit, Smith, sphenic, powerful, and several others. Each membership check is a pure function, deterministic, and individually unit-tested.
- Alternate representations — number-in-words and ordinal forms in the current language, Roman numerals (1–3,999), binary, octal, hexadecimal, Base64, one's complement at the smallest sufficient width.
- Historical numeral systems — Babylonian (base 60, cuneiform), Egyptian hieroglyphic, Greek (Milesian/alphabetic), Mayan (base 20), and Chinese (everyday and financial 大寫). Plus a compact strip of nine modern non-Latin decimal scripts: Eastern Arabic, Devanagari, Bengali, Tamil, Thai, Tibetan, Khmer, Lao, and Burmese. Each system is generated from the number, not stored. See the explainer articles linked below.
- Cultural significance — for numbers with documented meaning in world cultures (lucky in Chinese, unlucky in Italian, sacred in Hindu, slang in pop culture, etc.), we surface short notes per culture with the source. Hand-curated from public references; about 45 numbers have entries currently.
- Calendar conversions — for years 1–2100, the same year in eight other calendars: Hebrew (Anno Mundi), Islamic Hijri, Chinese zodiac (animal + element + sexagenary cycle position), Buddhist Era, Persian Solar Hijri, Ethiopian, Indian National (Saka), and Japanese reign-era.
- Year facts — for year pages, deterministic facts: leap-year status with its reason, day count, ISO week count, weekday of January 1 and December 31, Friday-the-13th count, Easter Sunday date (Gregorian computus), the year's decade / century / millennium, recurring cycles (US presidential election, FIFA World Cup, Olympics), and a "this year vs today" relative offset.
- Notable events — for ~660 years across 1500–2026 plus famous ancient years (e.g., 79 — Vesuvius; 1066 — Hastings; 44 BC — Caesar), a curated bullet timeline of three-to-five major events with their dates. Source material is Wikipedia's "Events" sections, condensed and rewritten into original short prose so we're not republishing copyrighted text.
- Pattern detectors — independent classifiers that fire when an integer matches a real-world pattern. Each rendered detector adds its own explanatory body to the page: HTTP status codes (RFC text + class), TCP/UDP ports (service and protocol), IPv4 addresses (dotted-quad, IPv6 mapping, RFC classification), Unicode codepoints (glyph, category, UTF-8 bytes), ASCII characters (control-character names), NANP area codes and phone numbers, US patent numbers (with estimated issue year), ABA routing numbers (with Federal Reserve district), hex color codes (with RGB and a colour swatch), Unix timestamps, geographic coordinates (named parallels and meridians), US Interstate and US Route highway designations, calculator-display words (digits that read as English when the display is flipped), credit-card BIN ranges, code-page identifiers, Goldbach decompositions for even numbers, prime neighbourhoods, the digit-at-position lookup in the first million digits of π, e, φ, √2, ln 2, and γ.
- Curated editorial — for ~27 famous numbers (and growing) we hand write an introductory note explaining what makes them special: 42 and the Hitchhiker's Guide; 1729 and Hardy-Ramanujan; 1337 and leetspeak; 86,400 and the seconds-in-a-day convention; etc. These notes have sources cited. Curated entries are translated into Spanish, French, and German.
Curation policy
A page is created when one of these is true:
- It's a year in 1–2100 AD or 1–3000 BC.
- It's a prime under 100,000 (initial seed; will expand).
- It's hand-curated as notable for cultural, technical, or historical reasons.
- It triggers a pattern detector (HTTP status, port, IPv4, area code, etc.) at high enough specificity.
Pages outside the index can still be rendered live — visit /12345 for any
non-negative integer and the same classification pipeline produces a page on the fly;
those live-analysis pages are marked noindex so they don't pollute the search index.
Internationalisation
UI chrome and detector explanations are translated into Spanish, French, and German
(with English fallback for missing strings). Per-language URLs are exposed as
/es/{n}, /fr/{n}, /de/{n} with proper hreflang
tags. Year summaries and curated content are translated where possible; some content
(sequence-membership prose for non-English number names, very obscure detector bodies)
still falls back to English.
Sources and attribution
- Mathematical content — pure functions, sourced from standard number-theory references (Hardy and Wright's An Introduction to the Theory of Numbers; OEIS A-numbers for sequences). Nothing scraped.
- Cultural notes — hand-compiled from Wikipedia ("Chinese numerology", "Numbers in Japanese culture", "Numerology", "Gematria", and per-number articles), with the source URL on each card.
-
Calendar conversions — algorithmic, using the BCL's
HijriCalendarandPersianCalendarclasses plus published constants (Buddhist Era, Anno Mundi, Saka, Ethiopian offsets, Chinese sexagenary cycle anchor). - Pattern-detector reference data — RFC numbers (HTTP status, IPv4 blocks, IANA port assignments) are public. NANP area codes and US Interstate routes are public. ABA routing-number Federal-Reserve districts are public. Where we use a bounded reference table, that table is committed to the repo and dated.
- Year events — derived from Wikipedia's per-year "Events" sections. The source text is fetched from the MediaWiki API, then condensed and rewritten into original short prose (under 100 chars per event) so the published content is ours, not Wikipedia's. The Wikipedia "Events compiled from" link credits the source. Wikipedia is licensed CC-BY-SA 4.0; attribution remains visible.
- Curated number notes — written from public sources. Each entry lists the URLs it consulted.
- Unicode reference data — official Unicode Character Database (categories, names) compiled into a static lookup table; updated when a new Unicode version ships.
Update cadence
Code updates are deployed continuously — typically multiple times per week. The curated-number list, cultural-significance dataset, and year-events corpus are updated as new entries are written. Year pages for the current year refresh whenever new events are added to the source. The site's "current year" reference (used in "X years ago" / "X years from now" facts) is read from the server clock at request time, so relative offsets stay accurate without redeploys.
Performance
Every page is output-cached for 24 hours after first render, varied by request culture. A cold render takes a few milliseconds; warm hits are sub-millisecond. The whole site runs on a single ASP.NET Core process; the database is SQLite. Embedded resources (the prime-table, math-constant digit files, Unicode-name table, year-events archive) ship inside the binary so a deploy is one tarball with no external dependencies.
Roadmap
Items in the active queue:
- Live search-any-number with on-the-fly classification (most of the pipeline already supports this).
- More identifier detection — ISBN check digits, UPC/EAN, IBAN, BIC, SWIFT, Luhn for non-cards.
- Expanded curated set (~200 entries vs the current 27).
- Pillar articles for each historical numeral system, each major sequence, and concept pages on prime, perfect, Mersenne, Fibonacci, etc.
- BC-year coverage in non-English languages.
- Dense coverage of every integer 0–10,000.
- Optional "history-of-this-day" surface drawing on the date metadata in the events corpus.
Who runs it
NumberWiki is built and maintained as an independent reference and wiki project. You can reach the team at contact@number.wiki. Bug reports, factual corrections, suggestions for numbers worth curating, and translation review are all welcome — see the contact page.
How to cite
Each number's URL is its citation:
https://number.wiki/{n}. URLs are stable — once a number is in the index,
its slug doesn't change. Localised variants are at https://number.wiki/<lang>/{n}.
Permalinks are also exposed in the <link rel="canonical"> tag and in
the page's Article JSON-LD.
Articles
Long-form explainers written for the site, newest first. We publish new pieces on a regular cadence — concept pages for the major number sequences and properties, and deep dives on the historical numeral systems. Check back for more.
- Numerals around the world — The non-Latin decimal scripts — Eastern Arabic, Devanagari, Thai, and more — that write the same base-10 numbers with different digits. · Numeral systems
- Chinese numerals — Everyday 一二三 and the fraud-resistant 大寫 financial characters used on cheques and contracts. · Numeral systems
- Musical pitch — How a frequency in hertz becomes a musical note in three tunings — with a playable keyboard and a clickable table of frequencies. · Concepts
- Greek numerals — The Milesian system that turned the alphabet into numbers, with distinct letters for ones, tens, and hundreds. · Numeral systems
- Roman numerals — The additive-subtractive letter system — I, V, X, L, C, D, M — still on clock faces, book chapters, and movie credits. · Numeral systems
- Triangular numbers — 1, 3, 6, 10, 15 … the counting numbers stacked into triangles, and Gauss's famous shortcut for summing them. · Concepts
- Amicable numbers — Pairs of numbers, each the sum of the other's divisors — a Pythagorean symbol of friendship. · Concepts
- Mersenne primes — Primes one less than a power of two — the record-holders for the largest known primes for over a century. · Concepts
- Perfect numbers — Numbers exactly equal to the sum of their parts — only 52 are known, and the odd ones may not exist at all. · Concepts
- Fibonacci numbers — The sequence where each term is the sum of the two before it — and why it turns up everywhere. · Concepts
- Prime numbers — The building blocks of arithmetic: what primes are, why they matter, and how we find them. · Concepts
- Mayan numerals — Vigesimal dots-and-bars with a shell zero — one of the earliest true zeros. · Numeral systems
- Egyptian hieroglyphic numerals — Seven hieroglyphs for every power of ten, from a single stroke to a million. · Numeral systems
- Babylonian numerals — The base-60 cuneiform system that gave us 60 minutes, 60 seconds, and 360°. · Numeral systems
Reference series
- ASCII characters — codepoints 0–127, each linking to its number page.
- All tags — browse numbers by sequence membership, primality class, or curated category.