Problem to download Kali Linux 64 bit ISO or 32 bit ISO ?

Hello.

I would like download Kali to install it on a USB PORTABLE but I notice on the download page for Kali https://www.kali.org/downloads/ that are 2 kinds of ISO which Kali Linux 64 bit ISO and Kali Linux 32 bit ISO. And then frankly I am confused.

Can you advise me which of the two (Kali Linux 64 bit ISO or Kali Linux 32 bit ISO), download and install it on my portable USB key so he walks or runs 100 % on any operating system without any problems ?

Thank you.