The CAS Registry Mumber 99049-56-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,9,0,4 and 9 respectively; the second part has 2 digits, 5 and 6 respectively. Calculate Digit Verification of CAS Registry Number 99049-56: (7*9)+(6*9)+(5*0)+(4*4)+(3*9)+(2*5)+(1*6)=176 176 % 10 = 6 So 99049-56-6 is a valid CAS Registry Number.