You copied the Doc URL to your clipboard.

Optional hash with immediate constants

You do not have to specify a hash before an immediate constant in any instruction syntax.

This applies to ARM, Thumb, Wireless MMX, NEON, and VFP instructions. For example, the following are valid instructions:

    BKPT 100
    MOVT R1, 256
    VCEQ.I8 Q1, Q2, 0    

By default, the assembler warns if you do not specify a hash:

WARNING: A1865W: '#' not seen before constant expression.

You can suppressed this with --diag_suppress=1865.

If you use the assembly code with another assembler, you are advised to use the # before all immediates. The disassembler always shows the # for clarity.