The CAS Registry Mumber 121258-01-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,1,2,5 and 8 respectively; the second part has 2 digits, 0 and 1 respectively. Calculate Digit Verification of CAS Registry Number 121258-01: (8*1)+(7*2)+(6*1)+(5*2)+(4*5)+(3*8)+(2*0)+(1*1)=83 83 % 10 = 3 So 121258-01-3 is a valid CAS Registry Number.