Letters and Sounds Seldom Used
The following are sometimes used and from their SOUND have digit value and should be noted for completeness:
Q sounds similar to K and is 7.
X is pronounced EKS, has the KS sound and is 70.
Hard Ch as in ACHE has the K sound and is 7.
Gh and Ph as in Cough and Phone have the F sound and are 8.
By using the suffix ING to represent 7, which is an arbitrary exception to fill a need, you can get a great deal of help in forming words for difficult numbers which end in 7, as 447 RoaRING, 117 DoTING, 577 LacKING, 397 MoPING.