Definition from Wiktionary, the free dictionary
|Unicode name||GREEK SMALL LETTER PHI|
- (mathematics) The golden ratio, an irrational number with a value of approximately 1.618033988 which expresses the relationship that the sum of two quantities is to the larger quantity as the larger is to the smaller.
φ (lowercase, uppercase Φ)
See also 
- The number 500 in Greek numerals.
- The number 500,000 in Greek numerals.