The CAS Registry Mumber 156532-80-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,6,5,3 and 2 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 156532-80: (8*1)+(7*5)+(6*6)+(5*5)+(4*3)+(3*2)+(2*8)+(1*0)=138 138 % 10 = 8 So 156532-80-8 is a valid CAS Registry Number.