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Properties of the Number 20821

Twenty Thousand Eight Hundred Twenty-One

Basics

Value: 20820 → 20821 → 20822

Parity: odd

Prime: No

Previous Prime: 20809

Next Prime: 20849

Digit Sum: 13

Digital Root: 4

Palindrome: No

Factorization: 47 × 443

Divisors: 1, 47, 443, 20821

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101000101010101

Octal: 50525

Duodecimal: 10071

Hexadecimal: 5155

Square: 433514041

Square Root: 144.29483705247392

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

Array read by antidiagonals: A(n,k) is the number of binary matrices with k columns and any number of nonzero rows with n ones in every column and columns in nonincreasing lexicographic order. A330942
Unlabeled version of A055203: number of different relations between n intervals (of nonzero length) on a line, up to permutation of intervals. A121316
Smallest j such that j·2*p(n)3-1=q is prime, j·2*p(n)*q2-1=r, j·2*p(n)*r2-1=s, where r and s are also prime. A224611
Decimal representation of the x-axis, from the left edge to the origin, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 99", based on the 5-celled von Neumann neighborhood. A278872
Decimal representation of the x-axis, from the origin to the right edge, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 203", based on the 5-celled von Neumann neighborhood. A279811
Numbers such that the digital sum base 2 and the digital sum base 3 and the digital sum base 4 all are equal. A135122
Alternating row sums of triangle A134280 (S2(6)'). A134282
Number of ordered triples (w,x,y) with all terms in {1,...,n} and w4<x4+y4. A211652
Smallest positive multiple of n whose base-4 representation contains only 0's and 1's. A244955
Triangle read by rows: number of generic n-rook placements with k rooks below the main diagonal. A269744