The CAS Registry Mumber 7107-04-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,1,0 and 7 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 7107-04: (6*7)+(5*1)+(4*0)+(3*7)+(2*0)+(1*4)=72 72 % 10 = 2 So 7107-04-2 is a valid CAS Registry Number.