The CAS Registry Mumber 74615-15-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,6,1 and 5 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 74615-15: (7*7)+(6*4)+(5*6)+(4*1)+(3*5)+(2*1)+(1*5)=129 129 % 10 = 9 So 74615-15-9 is a valid CAS Registry Number.