i-adjective
easy to ...; not difficult to ...
Bound adjective form used in the pattern 〜に難くない, meaning 'it is easy to ...' or 'it is not difficult to ...'. This is a literary or formal expression; in everyday speech, 〜やすい or 〜にくくない are more common.
彼の成功は想像に難くない。
His success is easy to imagine.
その結果は予測に難くない。
The result is not difficult to predict.