On your Android 6.0.1 browser, navigate to the APKMirror website. Search for "WhatsApp Messenger". Look for a version that explicitly states:
Instead of the Play Store, download the installer (APK) manually. Visit APKMirror. Search for "WhatsApp Messenger." download whatsapp for android 601 exclusive
: Older versions lack the latest security patches required to keep user data safe. On your Android 6
If the Play Store is unavailable, you can download the official installer (APK file) directly from the WhatsApp Android Website 2. Alternative: Manual APK Installation On your Android 6.0.1 browser
To download and use on a device running Android 6.0.1 (Marshmallow)