We cannot send a text message to this number.

if you are having this problem with your microsoft hotmail, live or outlook account on your PC suspending your account because you replied to a message that microsoft identified as spam even though it wasn't spam & it asking you to verify your phone number & then it tells you that number can not be contacted.

this is what I did on my windows 10 PC.

clear your cache

log-in to outlook.com

when it asks you to verify through an email address look to the bottom of the window, chose Sign in using a different method, chose send test message to ####
add the 4 numbers, you'll get a code.

hope this helps.
i had to read 1,500 messages on this site which were all 100% unhelpful, especially the one from Janbaz Salehi who told me to log into the account that "i was locked out of" & told to ad my phone number "to the account that I could not log into"

not very forward thinking Mr. Janbaz Salehi

thank you. your solution worked.

I solved my problem by similar way. I tried to logon to my account by using my Samsung phone's browser.

I had tried all the mentioned methods but still facing the same issue. Is there some other way to solve this issue.

I tried multiple phone numbers and clearing my browser cache (Chrome and Firefox) but with no success then thought I would give Edge ago and it managed to send the text message first time.

It might not work for everyone but it worked for me!

Thank you!! This worked for me.