The CAS Registry Mumber 13213-87-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,3,2,1 and 3 respectively; the second part has 2 digits, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 13213-87: (7*1)+(6*3)+(5*2)+(4*1)+(3*3)+(2*8)+(1*7)=71 71 % 10 = 1 So 13213-87-1 is a valid CAS Registry Number.