The CAS Registry Mumber 1491-68-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,4,9 and 1 respectively; the second part has 2 digits, 6 and 8 respectively. Calculate Digit Verification of CAS Registry Number 1491-68: (6*1)+(5*4)+(4*9)+(3*1)+(2*6)+(1*8)=85 85 % 10 = 5 So 1491-68-5 is a valid CAS Registry Number.