Properties of the Number 21985

Twenty-One Thousand Nine Hundred Eighty-Five

Basics

Value: 21984 → 21985 → 21986

Parity: odd

Prime: No

Previous Prime: 21977

Next Prime: 21991

Digit Sum: 25

Digital Root: 7

Palindrome: No

Factorization: 5 × 4397

Divisors: 1, 5, 4397, 21985

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2730 Try Today's Challenge

Representations

Binary: 101010111100001

Octal: 52741

Duodecimal: 10881

Hexadecimal: 55e1

Square: 483340225

Square Root: 148.27339613025663

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

Numbers k such that the continued fraction for sqrt(k) has period 81. A20420

n³ + n-th cubefree number. A180499

Number of 0..6 arrays of length n with each element differing from at least one neighbor by 1 or less, starting with 0. A221681

Expansion of ∏_k>=2 (1 + k·x^k). A317913

Number of compositions of n such that one maximal run is the longest. A391595

Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 32. A31620

Number of partitions in parts not of the form 17k, 17k+3 or 17k-3. Also number of partitions with at most 2 parts of size 1 and differences between parts at distance 7 are greater than 1. A35964

Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 1100-1111-0001 pattern in any orientation. A146851

T(n,k)=Number of 0..k arrays of length n with each element differing from at least one neighbor by 1 or less, starting with 0. A221683

Decimal expansion of 1/981. A21985