The CAS Registry Mumber 77599-10-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,5,9 and 9 respectively; the second part has 2 digits, 1 and 0 respectively. Calculate Digit Verification of CAS Registry Number 77599-10: (7*7)+(6*7)+(5*5)+(4*9)+(3*9)+(2*1)+(1*0)=181 181 % 10 = 1 So 77599-10-1 is a valid CAS Registry Number.