Who called from 2133781129

Didn't answer

Didn't answer no voicemail left

Called my cell number. I don't pick up unless I know the number. Don't know this one.

Received a call from this number, did not pick up. Caller did not leave a voicemail. Call seems to trace to Russia (?)

I have gotten calls from 213-378-1129 several times on my cell phone.  I got a call again today. I don't know this number and I never pick up.   There is never a message/voicemail.  So why do these calls continue?   I read online this number has been traced to Russia?  Really?  That's kind of scary!