The CAS Registry Mumber 18587-35-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,5,8 and 7 respectively; the second part has 2 digits, 3 and 5 respectively. Calculate Digit Verification of CAS Registry Number 18587-35: (7*1)+(6*8)+(5*5)+(4*8)+(3*7)+(2*3)+(1*5)=144 144 % 10 = 4 So 18587-35-4 is a valid CAS Registry Number.