The CAS Registry Mumber 3400-93-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,4,0 and 0 respectively; the second part has 2 digits, 9 and 3 respectively. Calculate Digit Verification of CAS Registry Number 3400-93: (6*3)+(5*4)+(4*0)+(3*0)+(2*9)+(1*3)=59 59 % 10 = 9 So 3400-93-9 is a valid CAS Registry Number.