Alright, let's work through 21387446 times 81503061 step by step
21387446 × 81503061 = 81503061 × (21387446)
+ 81503061 × 6 which equals 489018366
+ 81503061 × 40 that equals 3260122440
+ 81503061 × 400 that is equal 32601224400
+ 81503061 × 7000 that equals 570521427000
+ 81503061 × 80000 producing 6520244880000
+ 81503061 × 300000 producing 24450918300000
+ 81503061 × 1000000 yielding 81503061000000
+ 81503061 × 20000000 producing 1630061220000000

= 1743142315972206
