The Latin word quattuor
Word quattuor
Meaning four
See also Phrygian: *ΔΙΘΥΡ ‘four’
Phrygian: *ΘΙΔΡΑ- ‘four’
Avestan: caθβarasca ‘four’

Other words that might be of interest
ūnus ‘one’, duō ‘two’, trēs ‘three’, quīnque ‘five’