The CAS Registry Mumber 56059-55-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,6,0,5 and 9 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 56059-55: (7*5)+(6*6)+(5*0)+(4*5)+(3*9)+(2*5)+(1*5)=133 133 % 10 = 3 So 56059-55-3 is a valid CAS Registry Number.