The CAS Registry Mumber 62371-91-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,2,3,7 and 1 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 62371-91: (7*6)+(6*2)+(5*3)+(4*7)+(3*1)+(2*9)+(1*1)=119 119 % 10 = 9 So 62371-91-9 is a valid CAS Registry Number.