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 2026-07-28 · rubric v0.6
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 1
Open, tool-agnostic API collections (OpenAPI-derived and Bruno).
Numbers API
OPEN COLLECTIONFeatures 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 `