cisco confreg changing

i have a 2600 router, the configuration register was mistakenly changed to 0x2162 , but when i tried changing it to the default 0x2102, it will only changes to 0x2122. i tried all i could but it seems the 2 b4 the last will just not change to any value below 2.
what can be done to correct this and if nothing, what is the implication of leaving the confreg as 0x2122.