A palindromic number or numeral palindrome is a number that remains the same when its digits are reversed. Like 16461, for example, it is "symmetrical". The term palindromic is derived from palindrome, which refers to a word (such as rotor or racecar) whose spelling is unchanged when its letters are reversed. The first 30 palindromic numbers are:
- 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, X, E, 11, 22, 33, 44, 55, 66, 77, 88, 99, XX, EE, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 1X1, 1E1, 202, ...
Mod n[]
Pictorial representation of remainders (mod 1, 2, 3, ...,10) frequency for such numbers ≤ 106:
modulo | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 1EEX | |||||||||||
2 | XXX | 1110 | ||||||||||
3 | 666 | 888 | 888 | |||||||||
4 | 444 | 666 | 666 | 666 | ||||||||
5 | 499 | 49X | 4X7 | 48E | 489 | |||||||
6 | 222 | 444 | 444 | 444 | 444 | 444 | ||||||
7 | 365 | 358 | 345 | 346 | 36X | 337 | 345 | |||||
8 | 222 | 333 | 334 | 333 | 222 | 333 | 332 | 333 | ||||
9 | 222 | 2XE | 2XE | 222 | 2XE | 2XX | 222 | 2XX | 2XE | |||
X | 225 | 27X | 225 | 26E | 220 | 274 | 220 | 282 | 220 | 269 | ||
E | 222 | 222 | 222 | 222 | 222 | 222 | 222 | 222 | 222 | 222 | 222 | |
10 | 0 | 222 | 222 | 222 | 222 | 222 | 222 | 222 | 222 | 222 | 222 | 222 |
remainder | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | X | E |
A list for how many such numbers ≤ 106 are multiples of the numbers from 1 to 100.
+1 | +2 | +3 | +4 | +5 | +6 | +7 | +8 | +9 | +X | +E | +10 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|
0+ | 1EEX | XXX | 666 | 444 | 499 | 222 | 365 | 222 | 222 | 225 | 222 | 0 |
10+ | 10XE | 171 | 136 | 110 | 149 | 88 | 172 | X7 | E0 | E8 | 105 | 0 |
20+ | E5 | 5X5 | 88 | 81 | 104 | 4E | 93 | 67 | 70 | 7X | 88 | 0 |
30+ | 79 | 88 | 363 | 54 | 69 | 30 | 66 | 48 | 53 | 56 | 60 | 0 |
40+ | 59 | 53 | 46 | 242 | 54 | 2E | 55 | 41 | 52 | 54 | 45 | 0 |
50+ | 46 | 40 | 37 | 34 | 270 | 24 | 43 | 31 | 35 | 40 | 3E | 0 |
60+ | 40 | 39 | 2E | 35 | 3E | 121 | 34 | 28 | 2E | 32 | 35 | 0 |
70+ | 31 | 31 | 30 | 25 | 52 | 18 | 200 | 23 | 29 | 29 | 44 | 0 |
80+ | 23 | 27 | 25 | 21 | 2X | 16 | 26 | 121 | 21 | 24 | 28 | 0 |
90+ | 6 | 26 | 22 | 1X | 27 | 18 | 23 | 24 | 121 | 20 | 24 | 0 |
X0+ | 0 | 21 | 1X | 15 | 21 | 10 | E | 19 | 19 | 120 | 1E | 0 |
E0+ | 164 | 1X | 1X | 17 | 1E | E | 36 | 19 | 1X | 1E | 121 | 0 |