Using RegEx in find command

Below shown are the examples for using Regular Expression in 'find' command:

[ashok@linuxhost workdir]$ find . -type f -regex ".*[0-9]+.txt" -print 2> /dev/null
./1322143.txt
./anything_134.txt
./12345_837.txt
./something10984.txt

[ashok@linuxhost workdir]$ find . -type f -regex ".*/[0-9]+.txt" -print 2> /dev/null
./1322143.txt
[ashok@linuxhost workdir]$