The CAS Registry Mumber 6371-39-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,3,7 and 1 respectively; the second part has 2 digits, 3 and 9 respectively. Calculate Digit Verification of CAS Registry Number 6371-39: (6*6)+(5*3)+(4*7)+(3*1)+(2*3)+(1*9)=97 97 % 10 = 7 So 6371-39-7 is a valid CAS Registry Number.