Properties of the Number 1921

One Thousand Nine Hundred Twenty-One

Basics

Value: 1920 → 1921 → 1922

Parity: odd

Prime: No

Previous Prime: 1913

Next Prime: 1931

Digit Sum: 13

Digital Root: 4

Palindrome: No

Factorization: 17 × 113

Divisors: 1, 17, 113, 1921

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 11110000001

Octal: 3601

Duodecimal: 1141

Hexadecimal: 781

Square: 3690241

Square Root: 43.829214001622255

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

a(n) = ∑_{d divides n} q(d), where q(d) = A000009 = number of partitions of d into distinct parts. A47966

a(n) = 2·n² - 1. A56220

Numbers that are the sum of 2 positive 4th powers. A3336

Pentanacci numbers: a(n) = a(n-1) + a(n-2) + a(n-3) + a(n-4) + a(n-5) with a(0) = a(1) = a(2) = a(3) = a(4) = 1. A322

a(n) = least k such that the remainder when 9^k is divided by k is n. A127817

a(n) = least k such that the remainder when 12^k is divided by k is n. A127820

Number of twice-partitions of n with no repeated partitions. A296122

Centered 16-gonal numbers. A69129

Integers of the form m*(m + 6)/7. A274978

a(0) = 0 and then alternately even and odd numbers in increasing order such that the sum of any two successive terms is a square. A77221