exec format error (llvm-config) when installing numba on raspberry pi 3

I installed the aarch64 prebuilts for LLVM 5.0 on my raspeberry pi 3 and then did a 'pip3 install numba', pointing LLVM_CONFIG at the llvm-config executable. I get a exec format error when the install tries to execute llvm-config.

root@raspberrypi:/tmp# file /root/clang+llvm-5.0.0-aarch64-linux-
gnu/bin/llvm-config
/root/clang+llvm-5.0.0-aarch64-linux-gnu/bin/llvm-config: ELF 64-bit 
LSB executable, ARM aarch64, version 1 (SYSV), dynamically linked, 
interpreter /lib/ld-linux-aarch64.so.1, for GNU/Linux 3.7.0, not stripped

root@raspberrypi:/tmp# echo $LLVM_CONFIG
/root/clang+llvm-5.0.0-aarch64-linux-gnu/bin/llvm-config

root@raspberrypi:/tmp# /root/clang+llvm-5.0.0-aarch64-linux-
gnu/bin/llvm-config
bash: /root/clang+llvm-5.0.0-aarch64-linux-gnu/bin/llvm-config: cannot 
execute binary file: Exec format error

What am I doing wrong? Is aarch64 the wrong prebuilts to download for the pi3 ?