Dialing *#21# on your Android phone allows you to check the call forwarding settings on your device. It is important to note that the functionality of this code may vary depending on your service provider. Here is what dialing *#21# can do on your Android phone:

1. Check call forwarding status: Dialing *#21# will display the current call forwarding settings on your device. It will show whether your calls are being forwarded to another number or if call forwarding is disabled.

2. Verify unconditional call forwarding: If you are using a CDMA network like Verizon or US Cellular, dialing *21 will help you discover any unconditional call forwarding settings that may be enabled on your phone [1].

It is essential to understand that dialing *#21# does not reveal if your phone is being tapped or monitored. This code is primarily used to check call forwarding settings and does not provide any information about potential security breaches or surveillance activities on your device [2].

Learn more:

1. How to Tell If Your Phone Is Being Tapped: 10 Warning Signs
2. Fact check: Dialing this code does not show if your phone was tapped
3. Can Calling *#21# Reveal FBI iPhone Wiretap?