The CAS Registry Mumber 872705-64-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 8,7,2,7,0 and 5 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 872705-64: (8*8)+(7*7)+(6*2)+(5*7)+(4*0)+(3*5)+(2*6)+(1*4)=191 191 % 10 = 1 So 872705-64-1 is a valid CAS Registry Number.