numbers ∕ four-digit numbers 21xxtable of four-digit numbers (digits) ⫽ 2100 ― 219921x021x121x221x321x421x521x621x721x821x92100210121022103210421052106210721082109211021112112211321142115211621172118211921202121212221232124212521262127212821292130213121322133213421352136213721382139214021412142214321442145214621472148214921502151215221532154215521562157215821592160216121622163216421652166216721682169217021712172217321742175217621772178217921802181218221832184218521862187218821892190219121922193219421952196219721982199
@ifckr.v.0.