The CAS Registry Mumber 77526-59-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,5,2 and 6 respectively; the second part has 2 digits, 5 and 9 respectively. Calculate Digit Verification of CAS Registry Number 77526-59: (7*7)+(6*7)+(5*5)+(4*2)+(3*6)+(2*5)+(1*9)=161 161 % 10 = 1 So 77526-59-1 is a valid CAS Registry Number.