Alright, let's work through 6387963 times 77289421 step by step
6387963 × 77289421 = 77289421 × (6387963)
+ 77289421 × 3 giving us 231868263
+ 77289421 × 60 yielding 4637365260
+ 77289421 × 900 what gives us 69560478900
+ 77289421 × 7000 that equals 541025947000
+ 77289421 × 80000 what gives us 6183153680000
+ 77289421 × 300000 what gives us 23186826300000
+ 77289421 × 6000000 that results in 463736526000000

= 493721961639423
