The string command converts an expression to a string.
| string(ifactor(6)) | 
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This is the same thing as entering ifactor(6)+"", i.e. adding the empty string to the expression.
If you want to convert an unevaluated expression to a string, you can quote the expression (see Section 9.1.4):
| string(quote(ifactor(6))) | 
| 
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