The CAS Registry Mumber 39978-58-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,9,9,7 and 8 respectively; the second part has 2 digits, 5 and 8 respectively. Calculate Digit Verification of CAS Registry Number 39978-58: (7*3)+(6*9)+(5*9)+(4*7)+(3*8)+(2*5)+(1*8)=190 190 % 10 = 0 So 39978-58-0 is a valid CAS Registry Number.