The CAS Registry Mumber 83373-39-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,3,3,7 and 3 respectively; the second part has 2 digits, 3 and 9 respectively. Calculate Digit Verification of CAS Registry Number 83373-39: (7*8)+(6*3)+(5*3)+(4*7)+(3*3)+(2*3)+(1*9)=141 141 % 10 = 1 So 83373-39-1 is a valid CAS Registry Number.