The CAS Registry Mumber 65634-00-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,5,6,3 and 4 respectively; the second part has 2 digits, 0 and 0 respectively. Calculate Digit Verification of CAS Registry Number 65634-00: (7*6)+(6*5)+(5*6)+(4*3)+(3*4)+(2*0)+(1*0)=126 126 % 10 = 6 So 65634-00-6 is a valid CAS Registry Number.