The CAS Registry Mumber 15775-51-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,5,7,7 and 5 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 15775-51: (7*1)+(6*5)+(5*7)+(4*7)+(3*5)+(2*5)+(1*1)=126 126 % 10 = 6 So 15775-51-6 is a valid CAS Registry Number.