The CAS Registry Mumber 63674-71-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,3,6,7 and 4 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 63674-71: (7*6)+(6*3)+(5*6)+(4*7)+(3*4)+(2*7)+(1*1)=145 145 % 10 = 5 So 63674-71-5 is a valid CAS Registry Number.