You can do
dt[, !c("V1","V2","V3","V5")]
to get
V4 V6 V7 V8 V9 V10
1: 0.88612076 0.94727825 0.50502208 0.6702523 0.24186706 0.96263313
2: 0.11121752 0.13969145 0.19092645 0.9589867 0.27968190 0.07796870
3: 0.50179822 0.10641301 0.08540322 0.3297847 0.03643195 0.18082180
4: 0.09787517 0.07312777 0.88077548 0.3218041 0.75826099 0.55847774
5: 0.73475574 0.96644484 0.58261312 0.9921499 0.78962675 0.04976212
6: 0.88861117 0.85690337 0.27723130 0.3662264 0.50881663 0.67402625
7: 0.33933983 0.83392047 0.30701697 0.6138122 0.85107176 0.58609504
8: 0.89907094 0.61389815 0.19957386 0.3968331 0.78876682 0.90546328
9: 0.54136123 0.08274569 0.25190790 0.1920462 0.15142604 0.12134807
10: 0.36511064 0.88117171 0.05730210 0.9441072 0.40125023 0.62828674