The CAS Registry Mumber 85737-81-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,5,7,3 and 7 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 85737-81: (7*8)+(6*5)+(5*7)+(4*3)+(3*7)+(2*8)+(1*1)=171 171 % 10 = 1 So 85737-81-1 is a valid CAS Registry Number.