My phone constantly sends out texts to this number by itself????? Shows up as "hidden sender address" Tried calling the number. I am lead to believe that this is a hacker or scammer

is this a hacker or scam??? said 'anonymous' with a blank text. went call log and it gives me this number. 4433367363372337377

any help would be great...

I receive text messages from this number where the sender is hidden. message reads..
4504 message not found. When I go to the "view details" it reads.
Sender unknown, multi media, size 1kb