Numbertank is described as 'place to express yourself, discover yourself, and bond over the stuff you love. Whether it’s fandoms or philosophy, fashion or felines, Numbertank is where your interests connect you with your people' and is an app in the Network & Admin category. There are more than 25 alternatives to Numbertank for a variety of platforms, including Android, iPhone, Windows, Android Tablet and iPad. The best alternative is Telegram, which is free. Other great apps like Numbertank are Signal (Free, Open Source), WhatsApp (Free), Zulip (Free Personal, Open Source) and Viber (Freemium).
Signal is a messaging app with an unexpected focus on privacy, combined with all the features expected from a modern IM app. Signal has received a lot of praise from all around the world for its security and privacy-respecting technologies.
WhatsApp is an iPhone and Android messaging app which allows you to exchange messages without having to pay for SMS. In addition to basic messaging WhatsApp users can create groups, send each other unlimited images, video and audio media messages.
With Viber, everyone in the world can connect. Freely. More than 460 million Viber users text, make HD-quality phone and video calls, and send photo and video messages worldwide over WiFi or 3G - for free.
Conversations is a privacy focused, open source XMPP Texting [Jabber] client for Android 4.0+ smart phones with wife-approved easy encryption [OTR, OMEMO, or GPG]. [Note] **You can download the compiled apk for free from F-Droid**: ...
ChatSecure is a free and open source messaging app that features OTR encryption over XMPP. You can connect to your existing accounts on Facebook or Google, create new accounts on public XMPP servers(including via Tor), or even connect to your own server for extra security.