vCard Export Import(Lite) - vCard Export Import(Lite) app allows you to export your phone numbers in your contact list to the internal storage in vcard, vcf, txt, CSV, and various other file formats.

Share Contacts PRO - Share Contacts PRO app comes up with features to help users in editing a contact from your phonebook to change the name, phone number, address, and other details without much of a stretch.

rsync - rsync is a file transfer program for Unix systems. rsync uses the "rsync algorithm" which provides a very fast method for bringing remote files into sync.

Easy Contacts Backup & Restore - Easy Contacts Backup & Restore is an app by Future Tech that comes up with features to help you in saving your phone numbers in a backup file to restore the file in case of data deletion to get your deleted contacts back.

grsync - Grsync is a rsync gui, a graphical user interface for the rsync file synchronization and backup...

Duplicati - Free backup software to store backups online with strong encryption. Works with FTP, SSH, WebDAV, OneDrive, Amazon S3, Google Drive and many others.