- 45 is an odd composite number.
- 45 is the 9th triangular number.
- 45 is a solitary number.
- 45 RPM record was introduced on March 31, 1949 and soon replaced 78 RPM record.
In Greek-based number-naming systems, 45 is associated with prefix "pentatetraconta-", and with prefix "quinquadraginti-" in Latin systems.
As a banknote denomination
The third Burmese kyat had banknotes with this number in the denomination.
- Alan Cross. It was 70 years ago this month that the 45 RPM record was introduced, accidentally helping to give birth to rock’n’roll, Journal of Musical Things. March 17, 2019.