For example, 43210, 2222, 76652 and 9630 are all nialpdromes in base 10.
A nialpdrome in which the digits are strictly decreasing is called katadrome, while numbers whose digits are deincreasing and strictly decreasing are called plaindromes and metadromes.
The number of nialpdromes of
digits in base
is equal to
The total number of nialpdromes in base
with at most
digits is equal to
Probably the largest nialpdrome primes with index respectively
nialpdrome and plaindrome are and
.
See the plaindromes for the symmetric pairs.
The first nialpdromes (in base 10) are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 20, 21, 22, 30, 31, 32, 33, 40, 41, 42, 43, 44, 50 more terms
Below, the spiral pattern of nialpdromes up to 10000 . See the page on prime numbers for an explanation and links to similar pictures.