I could not find any information online (on Cisco's website or elsewhere) about the SRP547w's processor. You might be able to contact Cisco directly and ask for more detailed technical specifications than are available on their website.
I am fairly certain that the router will not be supported by OpenWRT. The Table of Hardware page on their wiki states:
A very reliable way to check for existing support, is to take a look at http://downloads.openwrt.org/snapshots/trunk/. The devices are sorted by target rather then manufacturer and if there is an image for the device, it should work
Unfortunately, neither the snapshots nor the various linked wiki pages contain any information about the SRP500 series, or any other similar Cisco small business router.