Prime String
Call a number 
a prime string from the left if and all numbers obtained by successively removing the rightmostDigit are Prime. There are 83 left prime strings in base 10. The first few are 2, 3, 5, 7, 23, 29, 31, 37, 53, 59,71, 73, 79, 233, 239, 293, 311, 313, 317, 373, 379, 593, 599, ... (Sloane's A024770), the largest being 73,939,133. Similarly,call a number a prime string from the right if and all numbers obtained by successively removing the left-mostDigit are Prime. The first few are 2, 3, 5, 7, 13, 17, 23, 37, 43, 47, 53, 67, 73, 83, 97, 103, 107, 113, 137, 167,173, ... (Sloane's A033664). A large right prime string is 933,739,397.
References
Beeler, M.; Gosper, R. W.; and Schroeppel, R. HAKMEM. Cambridge, MA: MIT Artificial Intelligence Laboratory, Memo AIM-239, Feb. 1972. Rivera, C. ``Problems & Puzzles (Puzzles): Prime Strings.'' http://www.sci.net.mx/~crivera/puzzles/puzz_002.htm. Sloane, N. J. A. Sequence A024770in ``The On-Line Version of the Encyclopedia of Integer Sequences.''http://www.research.att.com/~njas/sequences/eisonline.html.033664
- Parabolic Spindle Cyclide
- Parabolic Spiral
- Parabolic Umbilic Catastrophe
- Paraboloid
- Paraboloidal Coordinates
- Paraboloid Geodesic
- Paracompact Space
- Paracycle
- Paradox
- Paradromic Rings
- Paragyrate Diminished Rhombicosidodecahedron
- Parallel
- Parallel Axiom
- Parallel Class
- Parallel Curve
- Parallelepiped
- Parallelism
- Parallelizable
- Parallelogram
- Parallelogram Illusion
- Parallelogram Law
- Parallelohedron
- Parallelotope
- Parallel Postulate
- Parallel (Surface of Revolution)