Alright, let's work through 21020814 times 18741351 step by step
21020814 × 18741351 = 18741351 × (21020814)
+ 18741351 × 4 that equals 74965404
+ 18741351 × 10 that is equal 187413510
+ 18741351 × 800 what gives us 14993080800
+ 18741351 × 0000 resulting in 0
+ 18741351 × 20000 that results in 374827020000
+ 18741351 × 000000 that equals 0
+ 18741351 × 1000000 that results in 18741351000000
+ 18741351 × 20000000 yielding 374827020000000

= 393958453479714
