The CAS Registry Mumber 22743-80-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,2,7,4 and 3 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 22743-80: (7*2)+(6*2)+(5*7)+(4*4)+(3*3)+(2*8)+(1*0)=102 102 % 10 = 2 So 22743-80-2 is a valid CAS Registry Number.