Alright, let's work through 81016321 times 15210542 step by step
81016321 × 15210542 = 15210542 × (81016321)
+ 15210542 × 1 which equals 15210542
+ 15210542 × 20 what gives us 304210840
+ 15210542 × 300 that results in 4563162600
+ 15210542 × 6000 that equals 91263252000
+ 15210542 × 10000 that equals 152105420000
+ 15210542 × 000000 that results in 0
+ 15210542 × 1000000 yielding 15210542000000
+ 15210542 × 80000000 which equals 1216843360000000

= 1232302153255982
