The CAS Registry Mumber 131574-51-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,1,5,7 and 4 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 131574-51: (8*1)+(7*3)+(6*1)+(5*5)+(4*7)+(3*4)+(2*5)+(1*1)=111 111 % 10 = 1 So 131574-51-1 is a valid CAS Registry Number.