Assembly Cortex-M3 some Values being accepted, some not

i am completely new to assembly and i don't really understand why

MOV R0,#0xFFFFFFFF works compiles fine, but

MOV R0,#0x000FFFFF

produces this error:

"Immediate 0x000FFFFF cannot be represented by 0-255 shifted left by 0-23 or duplicated in all, odd or even bytes"

due to my missing knowledge, I cannot interpret / understand the error message. I have not shifted or anything else before the given statement.