The CAS Registry Mumber 552-76-1 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 5,5 and 2 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 552-76: (5*5)+(4*5)+(3*2)+(2*7)+(1*6)=71 71 % 10 = 1 So 552-76-1 is a valid CAS Registry Number.