The CAS Registry Mumber 517-37-3 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 5,1 and 7 respectively; the second part has 2 digits, 3 and 7 respectively. Calculate Digit Verification of CAS Registry Number 517-37: (5*5)+(4*1)+(3*7)+(2*3)+(1*7)=63 63 % 10 = 3 So 517-37-3 is a valid CAS Registry Number.