The CAS Registry Mumber 155740-04-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,5,7,4 and 0 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 155740-04: (8*1)+(7*5)+(6*5)+(5*7)+(4*4)+(3*0)+(2*0)+(1*4)=128 128 % 10 = 8 So 155740-04-8 is a valid CAS Registry Number.