The CAS Registry Mumber 19642-44-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,9,6,4 and 2 respectively; the second part has 2 digits, 4 and 4 respectively. Calculate Digit Verification of CAS Registry Number 19642-44: (7*1)+(6*9)+(5*6)+(4*4)+(3*2)+(2*4)+(1*4)=125 125 % 10 = 5 So 19642-44-5 is a valid CAS Registry Number.