For Windows Server 2016, the April 2017 cumulative update was KB4015217 (OS Build 14393.970).
Release date: April 11, 2017
Your string includes “2021.” If this image was created or modified in 2021, that means one of two things: windows server 2016 build 14393970 enus april 2017 2021
Do not use a pure April 2017 build (14393.970) on any network-connected system in 2025. It is missing: For Windows Server 2016, the April 2017 cumulative
If you found yourself on 14393.970 in 2021 or later, you had two primary paths: Do not use a pure April 2017 build (14393
Windows Server 2016 was released to manufacturing (RTM) on September 26, 2016, with build 14393.0. The versioning follows the pattern:
14393 = core RTM branch, .970 = cumulative update revision.