Properties of the Number 1561

One Thousand Five Hundred Sixty-One

Basics

Value: 1560 → 1561 → 1562

Parity: odd

Prime: No

Previous Prime: 1559

Next Prime: 1567

Digit Sum: 13

Digital Root: 4

Palindrome: No

Factorization: 7 × 223

Divisors: 1, 7, 223, 1561

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 11000011001

Octal: 3031

Duodecimal: AA1

Hexadecimal: 619

Square: 2436721

Square Root: 39.50949253027682

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

Central polygonal numbers: a(n) = n² - n + 1. A2061

Centered octahedral numbers (crystal ball sequence for cubic lattice). A1845

Number of partitions of n into parts 3k and 3k+1 with at least one part of each type. A35618

a(n) = C(n,1) + C(n,2) + C(n,3), or n*(n² + 5)/6. A4006

a(n) = 4·n² - 10·n + 7. A54554

a(n) = least m such that if a/b < c/d where a,b,c,d are integers in [0,n], then a/b < k/m < c/d for some integer k. A1000

Generalized 19-gonal (or enneadecagonal) numbers: m*(17·m - 15)/2 with m = 0, +1, -1, +2, -2, +3, -3, ... A303813

Generalized 17-gonal (or heptadecagonal) numbers: m*(15·m - 13)/2 with m = 0, +1, -1, +2, -2, +3, -3, ... A303305

Mountain numbers. A134941

Total number of ON cells at stage n of two-dimensional cellular automaton defined by "Rule 750" using the von Neumann neighborhood. A169707