The CAS Registry Mumber 126308-15-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,6,3,0 and 8 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 126308-15: (8*1)+(7*2)+(6*6)+(5*3)+(4*0)+(3*8)+(2*1)+(1*5)=104 104 % 10 = 4 So 126308-15-4 is a valid CAS Registry Number.