The CAS Registry Mumber 55652-03-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,5,6,5 and 2 respectively; the second part has 2 digits, 0 and 3 respectively. Calculate Digit Verification of CAS Registry Number 55652-03: (7*5)+(6*5)+(5*6)+(4*5)+(3*2)+(2*0)+(1*3)=124 124 % 10 = 4 So 55652-03-4 is a valid CAS Registry Number.