The CAS Registry Mumber 401817-76-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 4,0,1,8,1 and 7 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 401817-76: (8*4)+(7*0)+(6*1)+(5*8)+(4*1)+(3*7)+(2*7)+(1*6)=123 123 % 10 = 3 So 401817-76-3 is a valid CAS Registry Number.