The missile flew 787 km (489 miles) on a trajectory reaching an altitude of 2,111.5 km (1,312 miles), KCNA said.
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From middle school physics, without considering earth curve:
t=sqrt(8*h/g)=1313 s flight time, and this gives you the speed
Vv=t*g/2=6433 m/s
Vh=d/t=599.4 m/s
V=sqrt(Vh2+Vv2)=6461 m/s

When shooting at 45 degree, this will give you 4259 km distance.
Yes this missile has a range over 4000 km.