51 (number) Guide, Meaning , Facts, Information and Description
51 is the natural number following 50 and preceding 52.
| Cardinal | fifty-one |
| Ordinal | 51st (fifty-first) |
| Factorization | |
| Roman numeral | LI |
| Binary | 110011 |
| Hexadecimal | 33 |
Fifty-one is a pentagonal number as well as a centered pentagonal number (one of the few numbers to be both) and an 18-gonal number. It is also the 6th Motzkin number, telling the number of ways to draw non-intersecting chords between any six points on a circle's boundary, no matter where the points may be located on the boundary.
It is also:
- the atomic number of antimony.
- the code for international direct dial phone calls to Peru.
- the model number of the P-51 Mustang WWII fighter aircraft
- part of the title of a collection of stories by Lord Dunsany, Fifty-One Tales.
- Area 51, a parcel of U.S. military-controlled land in southern Nevada, apparently containing a secret aircraft testing facility.
- The year AD 51, 51 BC, and 1951.
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