The CAS Registry Mumber 142791-64-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,4,2,7,9 and 1 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 142791-64: (8*1)+(7*4)+(6*2)+(5*7)+(4*9)+(3*1)+(2*6)+(1*4)=138 138 % 10 = 8 So 142791-64-8 is a valid CAS Registry Number.