Properties of the Number 1805

One Thousand Eight Hundred Five

Basics

Value: 1804 → 1805 → 1806

Parity: odd

Prime: No

Previous Prime: 1801

Next Prime: 1811

Digit Sum: 14

Digital Root: 5

Palindrome: No

Factorization: 5 × 19 ²

Divisors: 1, 5, 19, 95, 361, 1805

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 11100001101

Octal: 3415

Duodecimal: 1065

Hexadecimal: 70d

Square: 3258025

Square Root: 42.485291572496

Classification

Fibonacci: No

Bell Number: No

Factorial Number: No

Regular Number: No

Perfect Number: No

Special

Kaprekar Constant: No

Munchausen Constant: No

Armstrong Number: No

Kaprekar Number: No

Catalan Number: No

Vampire Number: No

Taxicab Number: No

Super Prime: No

Friedman Number: No

Fermat Number: No

Cullen Number: No

OEIS Sequences

a(n) = n + (n+1)². A28387

Odd numbers of the form p^1+4k * r², where p is prime of the form 1+4m, r > 1, and gcd(p,r) = 1. (Euler's criteria for odd perfect numbers). A228058

The "comma sequence": the lexicographically earliest sequence of positive numbers with the property that the sequence formed by the pairs of digits adjacent to the commas between the terms is the same as the sequence of successive differences between the terms. A121805

Coordination sequence for 3D uniform tiling formed by stacking parallel layers of the 4.8.8 2D tiling (cf. A008576). A299259

a(n) = 5·n². A33429

Numbers m such that there are precisely 3 groups of order m. A55561

|First digit - second digit + third digit - fourth digit ...| = 12. A60980

a(n) = n² - n - 1. A165900

Number of integer partitions of n whose sequence of frequencies is strictly increasing. A100471

Concentric pentagonal numbers: floor( 5·n² / 4 ). A32527