The CAS Registry Mumber 219924-10-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,1,9,9,2 and 4 respectively; the second part has 2 digits, 1 and 0 respectively. Calculate Digit Verification of CAS Registry Number 219924-10: (8*2)+(7*1)+(6*9)+(5*9)+(4*2)+(3*4)+(2*1)+(1*0)=144 144 % 10 = 4 So 219924-10-4 is a valid CAS Registry Number.