Στο ελληνικό σύστημα αρίθμησης έχει αριθμητική αξία φ´=500.
Phi (uppercase Φ, lowercase φ, or math symbol ϕ), pronounced /ˈfaɪ/ fy or sometimes /ˈfiː/ fee in English, and [ˈfi] in modern Greek, is the 21st letter of the Greek alphabet. In modern Greek, it represents [f], a voiceless labiodental fricative.
In Ancient Greek it represented[pʰ], an aspirated voiceless bilabial plosive (from which English ultimately inherits the spelling “ph” in words derived from Greek). In the system of Greek numerals it has a value of 500 (φʹ) or 500,000 (͵φ). The Cyrillic letter Ef (Ф, ф) arose from Φ.