The CAS Registry Mumber 1005611-01-7 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,0,0,5,6,1 and 1 respectively; the second part has 2 digits, 0 and 1 respectively. Calculate Digit Verification of CAS Registry Number 1005611-01: (9*1)+(8*0)+(7*0)+(6*5)+(5*6)+(4*1)+(3*1)+(2*0)+(1*1)=77 77 % 10 = 7 So 1005611-01-7 is a valid CAS Registry Number.