No problem, we've got 1991 and 2173 to multiply
1991 × 2173 = 2173 × (1991)
+ 2173 × 1 what gives us 2173
+ 2173 × 90 yielding 195570
+ 2173 × 900 what gives us 1955700
+ 2173 × 1000 that is equal 2173000

= 4326443
