How can I type the Multiply symbol (“ד) on iPhone?

I was using speech recognition to send a message in WhatsApp, and when I said “multiplied by” this sign appeared:

I can’t remember seeing this symbol on the default iOS keyboards, so I wonder if there are other ways to input this character (and maybe other characters?) into the phone without using speech recognition.

There is a paid app, called unichar that allows for searching (and input) all of the Unicode characters

If you just need to search (and copy) some Unicode chars, you can use their web app at:
https://unichar.app/web/

For such characters you use an app like Unicode Pad. Or just copy/paste one from here × into a text replacement on your phone.