The CAS Registry Mumber 10041-05-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,0,0,4 and 1 respectively; the second part has 2 digits, 0 and 5 respectively. Calculate Digit Verification of CAS Registry Number 10041-05: (7*1)+(6*0)+(5*0)+(4*4)+(3*1)+(2*0)+(1*5)=31 31 % 10 = 1 So 10041-05-1 is a valid CAS Registry Number.