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Properties of the Number 21982

Twenty-One Thousand Nine Hundred Eighty-Two

Basics

Value: 21981 → 21982 → 21983

Parity: even

Prime: No

Previous Prime: 21977

Next Prime: 21991

Digit Sum: 22

Digital Root: 4

Palindrome: No

Factorization: 2 × 29 × 379

Divisors: 1, 2, 29, 58, 379, 758, 10991, 21982

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010111011110

Octal: 52736

Duodecimal: 1087A

Hexadecimal: 55de

Square: 483208324

Square Root: 148.26327933780502

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 σ(φ(k)) = σ(k) where σ is the sum of divisors function A000203 and φ is the Euler totient function A000010. A33631
Position of first appearance of each integer in A088568 (number of 1's minus number of 2's in first n terms of A000002). A288605
Least k such that the first k terms of the Kolakoski sequence (A000002) contain n more 2's than 1's. A25503
Place two n-gons with radii 1 and 2 concentrically, forming an annular area between them. Connect all the vertices with line segments that lie entirely within that area. Then a(n) is the number of regions in that figure. A337700
a(n) = n*(n2 - 3·n + 4). A242659
a(n) = index where A088568 (or equally A294448) first reaches or exceeds n in magnitude. A294449
a(0)=1; for n >= 1, a(n) is the number of subsets of [a(0), a(1), ..., a(n-1)] whose sum is equal to a(n-1). A265853
Numbers n such that σ(σ(φ(n))) = σ(σ(n)). A172466
Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 462", based on the 5-celled von Neumann neighborhood. A272311
Number of distinct ways of expressing n using only addition, multiplication (with all factors greater than 1), necessary parentheses, and the number 1. A373446