The CAS Registry Mumber 57699-56-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,7,6,9 and 9 respectively; the second part has 2 digits, 5 and 6 respectively. Calculate Digit Verification of CAS Registry Number 57699-56: (7*5)+(6*7)+(5*6)+(4*9)+(3*9)+(2*5)+(1*6)=186 186 % 10 = 6 So 57699-56-6 is a valid CAS Registry Number.