The CAS Registry Mumber 3285-52-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,2,8 and 5 respectively; the second part has 2 digits, 5 and 2 respectively. Calculate Digit Verification of CAS Registry Number 3285-52: (6*3)+(5*2)+(4*8)+(3*5)+(2*5)+(1*2)=87 87 % 10 = 7 So 3285-52-7 is a valid CAS Registry Number.