The CAS Registry Mumber 34580-20-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,4,5,8 and 0 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 34580-20: (7*3)+(6*4)+(5*5)+(4*8)+(3*0)+(2*2)+(1*0)=106 106 % 10 = 6 So 34580-20-6 is a valid CAS Registry Number.