In number theory, an equidigital number is a natural number in a given number base that has the same number of digits as the number of digits in its prime...

the base 10 repunit (101031 − 1)/9.[citation needed][needs update] Equidigital number Sándor & Crstici (2004) p.383 McDaniel, Wayne (1987). "The existence...

between twin primes; number that is the sum of 7 positive 5th powers. In decimal: equidigital number; when turned around, the number looks like a prime...

A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that...

economical number has been used for a frugal number, but also for a number which is either frugal or equidigital. Let b > 1 {\displaystyle b>1} be a number base...

_{\stackrel {p^{2}\,\mid \,n}{p{\text{ prime}}}}K_{b}(v_{p}(n)).} Equidigital number Frugal number Darling, David J. (2004). The universal book of mathematics:...

month, the number of pairs of rabbits is equal to the number of mature pairs (that is, the number of pairs in month n – 2) plus the number of pairs alive...

is an untouchable number. 1510 is a subprime number (1510 + 1 = 1511, which is a prime). 1510 is one less than an equidigital number. If one leading zero...

In mathematics, a Fermat number, named after Pierre de Fermat (1607–1665), the first known to have studied them, is a positive integer of the form: F n...

1024, 1029, 1215, 1250 (sequence A046759 in the OEIS). An equidigital number has the same number of digits as its prime factorization. The first in decimal:...

triangular number or triangle number counts objects arranged in an equilateral triangle. Triangular numbers are a type of figurate number, other examples...

In mathematics, a harshad number (or Niven number) in a given number base is an integer that is divisible by the sum of its digits when written in that...

In mathematics, a square number or perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with...

In number theory, a Carmichael number is a composite number ⁠ n {\displaystyle n} ⁠ which in modular arithmetic satisfies the congruence relation: b n...

In number theory, an n-smooth (or n-friable) number is an integer whose prime factors are all less than or equal to n. For example, a 7-smooth number is...

they were previously discovered in the 1730s by Minggatu. The n-th Catalan number can be expressed directly in terms of the central binomial coefficients...

In mathematics, an automorphic number (sometimes referred to as a circular number) is a natural number in a given number base b {\displaystyle b} whose...

A composite number is a positive integer that can be formed by multiplying two smaller positive integers. Accordingly it is a positive integer that has...

mathematics, a Mersenne prime is a prime number that is one less than a power of two. That is, it is a prime number of the form Mn = 2n − 1 for some integer...

mathematics and combinatorics, a centered hexagonal number, or centered hexagon number, is a centered figurate number that represents a hexagon with a dot in the...

In number theory, a semiperfect number or pseudoperfect number is a natural number n that is equal to the sum of all or some of its proper divisors. A...

In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number...

In number theory, an abundant number or excessive number is a positive integer for which the sum of its proper divisors is greater than the number. The...

In number theory, a happy number is a number which eventually reaches 1 when the number and when applicable, the sum of the square of each of its digits...

In number theory, an n-Knödel number for a given positive integer n is a composite number m with the property that each i < m coprime to m satisfies i...

composite number, or it is not, in which case it is a prime number. For example, 15 is a composite number because 15 = 3 · 5, but 7 is a prime number because...

In mathematics, a semiprime is a natural number that is the product of exactly two prime numbers. The two primes in the product may equal each other, so...

In number theory, a weird number is a natural number that is abundant but not semiperfect. In other words, the sum of the proper divisors (divisors including...

In mathematics, a pandigital number is an integer that in a given base has among its significant digits each digit used in the base at least once. For...

the number 1 differently than larger numbers, sometimes even not as a number at all. Euclid, for example, defined a unit first and then a number as a...