The CAS Registry Mumber 3753-64-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,7,5 and 3 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 3753-64: (6*3)+(5*7)+(4*5)+(3*3)+(2*6)+(1*4)=98 98 % 10 = 8 So 3753-64-8 is a valid CAS Registry Number.