Numbers API (Math.Tools)
PaidLiveLast verified 24 Sept 2026
Answers number-theory questions (prime, palindrome, factors), converts bases and spells numbers out.
Example request
curl -s -H 'Authorization: Bearer $API_KEY' 'https://math.tools/api/numbers/prime/is-prime?number=17'
Free tier, in plain English
No free tier found; the cheapest plan (Starter) is $4.99/month for 5,000 requests/day.
Alternatives in Encyclopedic
Get Started with Web3Bilingual Web3 lesson index, glossary lookups, search, and role-based learning paths, with source citations.FreeWikidataStructured facts and relationships about people, places and concepts from Wikimedia's public knowledge base.FreeWikipediaFull-text article content, search, metadata and page history from Wikipedia and other wikis.FreeWolframAlphaComputational answer engine returning direct answers, data, and visualizations for math and factual queries.Freemium