The CAS Registry Mumber 15175-21-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,5,1,7 and 5 respectively; the second part has 2 digits, 2 and 1 respectively. Calculate Digit Verification of CAS Registry Number 15175-21: (7*1)+(6*5)+(5*1)+(4*7)+(3*5)+(2*2)+(1*1)=90 90 % 10 = 0 So 15175-21-0 is a valid CAS Registry Number.