The CAS Registry Mumber 56059-61-1 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, 6 and 1 respectively. Calculate Digit Verification of CAS Registry Number 56059-61: (7*5)+(6*6)+(5*0)+(4*5)+(3*9)+(2*6)+(1*1)=131 131 % 10 = 1 So 56059-61-1 is a valid CAS Registry Number.