Properties of the Number 861

Eight Hundred Sixty-One

Basics

Value: 860 → 861 → 862

Parity: odd

Prime: No

Previous Prime: 859

Next Prime: 863

Digit Sum: 15

Digital Root: 6

Palindrome: No

Factorization: 3 × 7 × 41

Divisors: 1, 3, 7, 21, 41, 123, 287, 861

Polygonal

Triangular: Yes

Square: No

Pentagonal: No

Hexagonal: Yes

Heptagonal: No

Tetrahedral: No

Today's Target

8509 Try Today's Challenge

Representations

Binary: 1101011101

Octal: 1535

Duodecimal: 5B9

Hexadecimal: 35d

Square: 741321

Square Root: 29.34280150224242

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

Triangular numbers: a(n) = binomial(n+1,2) = n*(n+1)/2 = 0 + 1 + 2 + ... + n. A217

Hexagonal numbers: a(n) = n*(2·n-1). A384

Smith (or joke) numbers: composite numbers k such that sum of digits of k = sum of digits of prime factors of k (counted with multiplicity). A6753

a(n) = binomial(n,2): number of size-2 subsets of {0,1,...,n} that contain no consecutive integers. A161680

Triangular numbers (A000217) with prime indices. A34953

Number of connected strict integer partitions of n. A304714

Average of twin prime pairs (A014574), divided by 2. Equivalently, 2·a(n)-1 and 2·a(n)+1 are primes. A40040

Number of partitions of n that do not contain 2 as a part. A27336

Numbers that are the sum of 11 positive 5th powers. A3356

Starting at n, a(n) is the total number of moves made to the right according to the following rules. On the k-th step (k=1,2,3,...) move a distance of k in the direction of zero. If the number landed on has been landed on before, move a distance of k away from zero instead. A324660