No problem, we've got 1661 and 7639 to multiply
1661 × 7639 = 7639 × (1661)
+ 7639 × 1 resulting in 7639
+ 7639 × 60 resulting in 458340
+ 7639 × 600 giving us 4583400
+ 7639 × 1000 that results in 7639000

= 12688379
