The CAS Registry Mumber 65628-42-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,5,6,2 and 8 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 65628-42: (7*6)+(6*5)+(5*6)+(4*2)+(3*8)+(2*4)+(1*2)=144 144 % 10 = 4 So 65628-42-4 is a valid CAS Registry Number.