Properties of the Number 2145

Two Thousand One Hundred Forty-Five

Basics

Value: 2144 → 2145 → 2146

Parity: odd

Prime: No

Previous Prime: 2143

Next Prime: 2153

Digit Sum: 12

Digital Root: 3

Palindrome: No

Factorization: 3 × 5 × 11 × 13

Divisors: 1, 3, 5, 11, 13, 15, 33, 39, 55, 65

Polygonal

Triangular: Yes

Square: No

Pentagonal: No

Hexagonal: Yes

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 100001100001

Octal: 4141

Duodecimal: 12A9

Hexadecimal: 861

Square: 4601025

Square Root: 46.314144707637645

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

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

The squarefree numbers ordered lexicographically by their prime factorization (with factors written in decreasing order). a(n) = ∏_{k in I} prime(k+1), where I is the set of indices of nonzero binary digits in n = ∑_{k in I} 2^k. A19565

Tritriangular numbers: a(n) = binomial(binomial(n,2),2) = n*(n+1)*(n-1)*(n-2)/8. A50534

Triangle of Bessel numbers read by rows: T(n,k) is the number of k-matchings of the complete graph K(n). A100861

Numbers whose base-2 representation is the juxtaposition of two identical strings. A20330

Numbers of the form 9·k² + 8·k, k an integer. A218864

Smallest j with n nodes in its riff (rooted index-functional forest). A62860

Numbers whose binary expansion is properly periodic. A121016

a(1)=1, a(n)=a(n-1)+n if n odd, a(n)=a(n-1)+ n² if n is even. A140113

3 times pentagonal numbers: 3·n*(3·n-1)/2. A62741