The CAS Registry Mumber 83703-55-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,3,7,0 and 3 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 83703-55: (7*8)+(6*3)+(5*7)+(4*0)+(3*3)+(2*5)+(1*5)=133 133 % 10 = 3 So 83703-55-3 is a valid CAS Registry Number.