Alright, let's work through 20787184 times 78915807 step by step
20787184 × 78915807 = 78915807 × (20787184)
+ 78915807 × 4 that results in 315663228
+ 78915807 × 80 what gives us 6313264560
+ 78915807 × 100 yielding 7891580700
+ 78915807 × 7000 what gives us 552410649000
+ 78915807 × 80000 yielding 6313264560000
+ 78915807 × 700000 that is equal 55241064900000
+ 78915807 × 0000000 which equals 0
+ 78915807 × 20000000 that is equal 1578316140000000

= 1640437400617488
