The CAS Registry Mumber 1487-91-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,4,8 and 7 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 1487-91: (6*1)+(5*4)+(4*8)+(3*7)+(2*9)+(1*1)=98 98 % 10 = 8 So 1487-91-8 is a valid CAS Registry Number.