---
tag: 8N1D20ZZTN
kind: concept
name: Keith number
aliases: [keith-numbers, keith-prime, repfigit, repfigit-number]
sources:
  - wikipedia: en:485251@r1325909713
    locator: Keith number
    note: adopted
    mention: wikipedia://en/485251
    sections: [Summary]
same_as:
  wikidata: Q378067
  wikipedia: Keith number
inventory: [26DKHZHD0Q]
---

## Summary

In recreational mathematics, a **Keith number** or **repfigit number** (short for **rep**etitive [[**F**ibonacci-like|0GA9K57A39]] d**igit**) is a [[natural number|0MWKJ44V5A]] $n$ in a given number base $b$ with $k$ digits such that when a sequence is created such that the first $k$ terms are the $k$ digits of $n$ and each subsequent term is the sum of the previous $k$ terms, $n$ is part of the sequence. Keith numbers were introduced by Mike Keith in 1987. They are computationally very challenging to find, with only about 125 known.