Even if you successfully install the app, you may face modern service issues: Whatsapp & Viber on OS 4.2.1 - Apple Support Community
Before hunting down a , understand the implications:
Are you trying to or use it as a daily driver ?
Modern web security (SSL/TLS) is often too advanced for the Safari browser on iOS 4, making it hard to download files directly.
Installing Viber on (common on the iPhone 3G and 2nd Gen iPod Touch) is no longer officially supported and is quite difficult in 2026. The current App Store version requires much newer software, and official support for iOS 4 ended over a decade ago. Apple Support Community Performance & Compatibility Review Official Incompatibility