2000 \times 2^6 = 128000.
It is informative because one can estimate how far each sensor can be pushed using simple heuristics.
I usually think like this: a current full frame sensor can be pushed to ISO 32000 without any problems using denoising current denoising algorithms. APS-C makes it 16000, the fact that it is a bit older makes it 8000.
So, you would need to exposure time and aperture to get more light. It is unclear why this shot needed a 138mm equiv focal length, which, with this lens, gives you f/5.6. If you want to capture shots like this, I would go for a bright prime, eg the 50mm f/1.8 which you can get for around 50 EUR for F-mount. Then you would have about 10 times the light, so if you expose for 1/50s you could shoot the same scene at effective 1000 ISO.
Or use a tripod and 1/5s exposure.
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