Alright, let's work through 90400503 times 79798331 step by step
90400503 × 79798331 = 79798331 × (90400503)
+ 79798331 × 3 producing 239394993
+ 79798331 × 00 giving us 0
+ 79798331 × 500 which equals 39899165500
+ 79798331 × 0000 what gives us 0
+ 79798331 × 00000 that equals 0
+ 79798331 × 400000 yielding 31919332400000
+ 79798331 × 0000000 which equals 0
+ 79798331 × 90000000 yielding 7181849790000000

= 7213809260960493
