The CAS Registry Mumber 97512-81-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,7,5,1 and 2 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 97512-81: (7*9)+(6*7)+(5*5)+(4*1)+(3*2)+(2*8)+(1*1)=157 157 % 10 = 7 So 97512-81-7 is a valid CAS Registry Number.