user1760: The title is the question :)
All the addresses I have seen - from the very first block http://blockexplorer.com/b/0 to the very last one http://blockexplorer.com/b/229850 all begin with "1".
Why is that? And - if it's really like that - why do we need the redundant number there and not just cut it and make the addresses 1 letter shorter?

user2785: If an address begin with "1" then it's a hash of a public key, "3" for a script hash, "5" for a private uncompressed key, etc
You can find a list of all prefixes here: https://en.bitcoin.it/wiki/List_of_address_prefixes

1760: <p>The title is the question :)</p>

<p>All the addresses I have seen - from the very first block <a href="http://blockexplorer.com/b/0">http://blockexplorer.com/b/0</a> to the very last one <a href="http://blockexplorer.com/b/229850">http://blockexplorer.com/b/229850</a> all begin with "1".</p>

<p>Why is that? And - if it's really like that - why do we need the redundant number there and not just cut it and make the addresses 1 letter shorter?</p>
 2785: <p>If an address begin with "1" then it's a hash of a public key, "3" for a script hash, "5" for a private uncompressed key, etc</p>

<p>You can find a list of all prefixes here: <a href="https://en.bitcoin.it/wiki/List_of_address_prefixes">https://en.bitcoin.it/wiki/List_of_address_prefixes</a></p>
