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Properties of the Number 1821

One Thousand Eight Hundred Twenty-One

Basics

Value: 1820 → 1821 → 1822

Parity: odd

Prime: No

Previous Prime: 1811

Next Prime: 1823

Digit Sum: 12

Digital Root: 3

Palindrome: No

Factorization: 3 × 607

Divisors: 1, 3, 607, 1821

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 11100011101

Octal: 3435

Duodecimal: 1079

Hexadecimal: 71d

Square: 3316041

Square Root: 42.67317658670374

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

Mian-Chowla sequence (a B2 sequence): a(1) = 1; for n>1, a(n) = smallest number > a(n-1) such that the pairwise sums of elements are all distinct. A5282
Number of partitions of n with distinct parts p(i) such that if i ≠ j, then |p(i) - p(j)| >= 3. A25157
Numbers k such that there is exactly one prime-power between prime(k)+1 and prime(k+1)-1. A377287
Number A(n,k) of n-length words w over a k-ary alphabet {a1,a2,...,ak} such that #(w,a1) >= #(w,a2) >= ... >= #(w,ak) >= 0, where #(w,x) counts the letters·in word w; square array A(n,k), n>=0, k>=0, read by antidiagonals. A226873
Triangle of numbers T(n,k) = number of permutations of (1,2,...,n) with longest increasing subsequence of length k (1<=k<=n). A47874
Triangle of numbers T(n,k) (n>=0, n>=k>=0) of transitive reflexive early confluent binary relations R on n labeled elements where k=maxx(|{y : xRy}|), read by rows. A135313
Number of non-isomorphic intersecting multiset partitions of weight n whose dual is also an intersecting multiset partition. A319765
Triangle read by rows giving the coefficients of formulas generating each variety of S1(n,k) (unsigned Stirling numbers of first kind). The p-th row (p>=1) contains T(i,p) for i=1 to 2·p, where T(i,p) satisfies ∑i=1..2·p T(i,p) * C(n,i). A94216
Numbers that are the sum of 3 nonzero squares in exactly 9 ways. A25329
Numbers which yield a prime whenever a 1 is inserted anywhere in them (including at the beginning or end). A68679