Properties of the Number 11781

Eleven Thousand Seven Hundred Eighty-One

Basics

Value: 11780 → 11781 → 11782

Parity: odd

Prime: No

Previous Prime: 11779

Next Prime: 11783

Digit Sum: 18

Digital Root: 9

Palindrome: No

Factorization: 3 ² × 7 × 11 × 17

Divisors: 1, 3, 7, 9, 11, 17, 21, 33, 51, 63

Polygonal

Triangular: Yes

Square: No

Pentagonal: No

Hexagonal: Yes

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 10111000000101

Octal: 27005

Duodecimal: 6999

Hexadecimal: 2e05

Square: 138791961

Square Root: 108.54031509075327

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

Doubly triangular numbers: a(n) = n*(n+1)*(n²+n+2)/8. A2817

Multiples of 17 containing a 17 in their decimal representation. A121037

a(n) = (2·n+1)*(4·n+1). A14634

Triangular numbers that are the product of two triangular numbers greater than 1. A188630

Number of integer partitions of n with integer reverse-alternating product. A347445

Molien series for cyclic group of order 5. A8646

a(n) = the least integer that is polygonal in exactly n ways. A63778

Odd octagonal numbers: (2n+1)*(6n+1). A14641

Numbers n for which nontrivial positive magic squares of exactly 10 different orders with magic sum n exist. For a definition of nontrivial positive magic squares, see A125005. A125017

Numbers m such that 3·m+1 and 8·m+1 are both squares. A245031