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...

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...

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

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...

_{\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:...

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...

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...

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...

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...

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...

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

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

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...

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...

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 number theory, a happy number is a number which eventually reaches 1 when the number is replaced by the sum of the square of each digit. For instance...

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

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...

algebra, the cube of a number n is its third power, that is, the result of multiplying three instances of n together. The cube of a number n is denoted n3,...

In mathematics, a Fermat number, named after Pierre de Fermat (1601–1665), the first known to have studied them, is a positive integer of the form: F n...

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 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...

A pronic number is a number that is the product of two consecutive integers, that is, a number of the form n ( n + 1 ) {\displaystyle n(n+1)} . The study...

In number theory, a lucky number is a natural number in a set which is generated by a certain "sieve". This sieve is similar to the sieve of Eratosthenes...

A tetrahedral number, or triangular pyramidal number, is a figurate number that represents a pyramid with a triangular base and three sides, called a tetrahedron...

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...