Reference for the p-adic numbers

Question

Can anyone give me a reference (book or a paper) that introduces the p-adic numbers and their important properties? Also, I would love if that reference contained some not to advanced applications of the p-adic numbers to number theory.

Thank you in advance!

Answer 1

p-adic Numbers, p-adic Analysis, and Zeta-Functions, Neal Koblitz (1984, ISBN 978-0-387-96017-3)

This is a short book. If you wish, you can only read the first chapter with 20 pages.

Answer 2

The book by Fernando Gouvea called 'p-adic numbers: an introduction' is quite nice elementary book for p-adic numbers.