Understanding sampling rate conversion
You would upsample by 441 and downsample by 640 since $11025 \cdot 640 = 16000 \cdot 441$

That would be a rather expensive operation, so in practice you would either fugde it a bit: 31/45 would get you to 11022Hz and 11/16 to 11000 Hz or you would use a suitable poly-phase irrational conversion algorithm