K21 
- TYPE: Submarine
- DISPLACEMENT SURFACED: 1,490 t (1,514 tnes)
- DISPLACEMENT SUBMERGED: 2,104 t (2,138 tnes)
- MACHINERY: Two Screws, Diesel/Electric Motors;
8,400/2,400 hp - LENGTH: 320.2 ft (97.65 m)
- BEAM: 24.25 ft (7.4 m)
- DRAUGHT: 14.83 ft (4.51 m)
- PERFORMANCE SURFACED: 21 knots
- PERFORMANCE SUBMERGED: 10 knots
- ARMAMENT: 10 533mm TT; 2 100mm guns;
20 mines - SURFACE RANGE: 12,000 nm (22,236 km)
at 9 knots - CREW: 60
- LAUNCHED: 1938