The CAS Registry Mumber 58215-80-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,8,2,1 and 5 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 58215-80: (7*5)+(6*8)+(5*2)+(4*1)+(3*5)+(2*8)+(1*0)=128 128 % 10 = 8 So 58215-80-8 is a valid CAS Registry Number.