The CAS Registry Mumber 150178-55-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,0,1,7 and 8 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 150178-55: (8*1)+(7*5)+(6*0)+(5*1)+(4*7)+(3*8)+(2*5)+(1*5)=115 115 % 10 = 5 So 150178-55-5 is a valid CAS Registry Number.