Number formatting

I am using the lookup formula to find a number in another coloumn. Once that is done, I want it to add ":1" to the end of the number.

Something like =LOOKUP(B47,$A$37:$A$43,$C$37:$C$43)":1"

Would find:
2
3
4
5

Would give output:
2:1
3:1
4:1
5:1

Thanks for the help!