Numbers API
Numbers API by David Hu and Mack Duan — a free, community-contributed HTTP API for interesting facts about numbers. Returns trivia, math, date, and year facts as plain text or JSON. Supports random numbers, ranges/batches, JSONP callbacks, document.write embedding, sentence-fragment responses, and configurable not-found behavior.
Numbers API publishes 5 APIs on the APIs.io network, including Batch API, Date API, Math API, and 2 more. Tagged areas include Science And Math, Public APIs, Trivia, Numbers, and Dates.
The Numbers API catalog on APIs.io includes 1 JSON-LD context and 2 Spectral governance rulesets.
Numbers API’s developer surface includes documentation, engineering blog, and 8 more developer resources.
Kin Score
Kin Score
How this is scored →scored 2026-08-20 · rubric v0.12.0
APIs 5
Individual APIs this provider publishes, each with its own machine-readable definition.
Numbers API Batch API
Multiple facts returned in a single request as a JSON map.
Numbers API Date API
Historical facts associated with a day of the year.
Numbers API Math API
Mathematical properties of integers.
Numbers API Trivia API
Trivia facts about integers.
Numbers API Year API
Historical facts associated with a year.
Open Collections 7
Open, tool-agnostic API collections (OpenAPI-derived and Bruno).
API Collection
OPEN COLLECTIONNumbers Batch API
OPEN COLLECTIONNumbers Batch Date API
OPEN COLLECTIONNumbers Batch Math API
OPEN COLLECTIONNumbers Batch Trivia API
OPEN COLLECTIONNumbers Batch Year API
OPEN COLLECTIONNumbers API
OPEN COLLECTIONScroll for all 7
Features 12
Notable capabilities this provider offers.
Trivia Facts
Return a piece of trivia about a number, e.g. `42 is the number of little squares forming the left side trail of Microsoft's Windows 98 logo`.
Math Facts
Return a mathematical property of a number, e.g. `5 is the number of platonic solids`.
Date Facts
Return a fact about a day of the year (month/day), e.g. `February 29 is the day in 1504 that Christopher Columbus uses his knowledge of a lunar eclipse to convince Native Americ...
Year Facts
Return a fact about a year, e.g. `1969 is the year that an estimated 500 million people worldwide watch Neil Armstrong take his historic first steps on the Moon`.
Random Numbers
Use the keyword `random` in place of a number to get a random fact, optionally bounded by `min` and `max` query parameters.
JSON Responses
Append `?json` (or send `Content-Type: application/json`) to receive the fact wrapped in an object with `text`, `found`, `number`, `type`, and optional `date`/`year` fields.
Sentence Fragment Mode
Append `?fragment` to get the fact rephrased as a lowercase, no- terminal-punctuation fragment suitable for embedding in a larger sentence.
Configurable Not Found Behavior
Use `notfound=default|floor|ceil` to control what happens when no fact exists for the requested number, with an optional custom `default=...` message.
JSONP Callback
Pass `callback=functionName` to wrap the response in a JSONP function call.
Document.write Embed
Pass `write` to wrap the response in `document.write(...)`, allowing a single `