with what number do multisig addresses (non-P2SH) start? I have never seen a n-m address implemented as multisig (not P2SH). What number does it start with (i.e., regular addresses start with 1, p2sh start with 3 ...) ? 

In other words, where do they fit in this table: https://en.bitcoin.it/wiki/List_of_address_prefixes?
There is no address type defined for raw multisig. If you want to send money to them, you'll need to construct the scriptPubKeys manually, or use the payment protocol (BIP 70-72).

In general, raw multisig is discouraged as it stores more data than necessary in the UTXO set (the database that all full nodes must maintain to be able to validate transactions).