Linked from
The 15 pages that link to p-adic number, each with the reason it gives.
Helmut HasseRelated: These numbers provide the local settings central to Hasse’s arithmetic methods.
Arithmetic geometryRelated: P-adic solutions capture behavior near a chosen prime.
Hensel's lemmaRelated: Hensel developed the lemma as a tool for working with these number systems.
Leopoldt's conjectureRelated: Local units are formed in completions of the field at primes above p.
Ostrowski's theoremRelated: Each prime-indexed class gives a corresponding p-adic completion.