Alright, let's work through 21615413 times 64138044 step by step
21615413 × 64138044 = 64138044 × (21615413)
+ 64138044 × 3 resulting in 192414132
+ 64138044 × 10 producing 641380440
+ 64138044 × 400 that results in 25655217600
+ 64138044 × 5000 producing 320690220000
+ 64138044 × 10000 what gives us 641380440000
+ 64138044 × 600000 that results in 38482826400000
+ 64138044 × 1000000 which equals 64138044000000
+ 64138044 × 20000000 which equals 1282760880000000

= 1386370310072172
