The CAS Registry Mumber 157142-64-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,7,1,4 and 2 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 157142-64: (8*1)+(7*5)+(6*7)+(5*1)+(4*4)+(3*2)+(2*6)+(1*4)=128 128 % 10 = 8 So 157142-64-8 is a valid CAS Registry Number.