The CAS Registry Mumber 194542-56-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,9,4,5,4 and 2 respectively; the second part has 2 digits, 5 and 6 respectively. Calculate Digit Verification of CAS Registry Number 194542-56: (8*1)+(7*9)+(6*4)+(5*5)+(4*4)+(3*2)+(2*5)+(1*6)=158 158 % 10 = 8 So 194542-56-8 is a valid CAS Registry Number.