The CAS Registry Mumber 135587-00-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,5,5,8 and 7 respectively; the second part has 2 digits, 0 and 0 respectively. Calculate Digit Verification of CAS Registry Number 135587-00: (8*1)+(7*3)+(6*5)+(5*5)+(4*8)+(3*7)+(2*0)+(1*0)=137 137 % 10 = 7 So 135587-00-7 is a valid CAS Registry Number.