All SMS Central dedicated numbers are sorted into Gold, Silver and Standard categories to differentiate the "quality" of these numbers. A number rated at a higher category is easier to remember and to identify than that of a lower category.
The quality of a number is determined by:
 How many sequential digits the number has
 How many identical digits the number has
 The number of patterns in the number
The following reference chart explains the categories and provides some examples (bookmark it for future reference!);
Number Category 
Type 
Example 
Gold 
6 of the same 
0400 222 222 
6 in sequence 
0400 123 456 

2 identical triplets 
0400 420 420 

Double Triplets 
0400 444 222 

3 identical pairs 
0400 42 42 42 

Silver 
5 of the Same 
0400 199 999 
5 in Sequence 
0400 412 345 

Identical pairs (same position) 
0400 001 002 

3 pairs 
0400 11 22 88 

Mirror Image 
0400 350 053 

1 triplet and 3 in sequence 
0400 123 8880400 777 234 

Standard 
Randomly generated 
0400 583 127 
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