Auto RP Multicast Router Settings

Finding auto-rp multicast port number, without memorizing the numbers

sh ip mroute

Outgoing interface flags: H - Hardware switched, A - Assert winner
 Timers: Uptime/Expires
 Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 224.0.1.39), 00:04:18/stopped, RP 0.0.0.0, flags: DCL
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    Vlan123, Forward/Sparse-Dense, 00:03:07/00:00:00
    Loopback0, Forward/Sparse-Dense, 00:04:18/00:00:00

(*, 224.0.1.40), 00:04:20/stopped, RP 0.0.0.0, flags: DCL
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    Loopback0, Forward/Sparse-Dense, 00:04:20/00:00:00

224.0.1.39 rp-announce
224.0.1.40 rp-discovery