The CAS Registry Mumber 6515-64-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,5,1 and 5 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 6515-64: (6*6)+(5*5)+(4*1)+(3*5)+(2*6)+(1*4)=96 96 % 10 = 6 So 6515-64-6 is a valid CAS Registry Number.