The CAS Registry Mumber 16652-36-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,6,6,5 and 2 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 16652-36: (7*1)+(6*6)+(5*6)+(4*5)+(3*2)+(2*3)+(1*6)=111 111 % 10 = 1 So 16652-36-1 is a valid CAS Registry Number.