The CAS Registry Mumber 68172-10-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,8,1,7 and 2 respectively; the second part has 2 digits, 1 and 0 respectively. Calculate Digit Verification of CAS Registry Number 68172-10: (7*6)+(6*8)+(5*1)+(4*7)+(3*2)+(2*1)+(1*0)=131 131 % 10 = 1 So 68172-10-1 is a valid CAS Registry Number.