The CAS Registry Mumber 125213-80-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,5,2,1 and 3 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 125213-80: (8*1)+(7*2)+(6*5)+(5*2)+(4*1)+(3*3)+(2*8)+(1*0)=91 91 % 10 = 1 So 125213-80-1 is a valid CAS Registry Number.