Properties of the Number -1721

Seven Hundred Twenty-One

Basics

Value: -1722 → -1721 → -1720

Parity: odd

Prime: No

Previous Prime:

Next Prime: 1

Digit Sum: 11

Digital Root: 2

Palindrome: No

Factorization: 1721

Divisors: 1, 1721

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: -11010111001

Octal: -3271

Duodecimal: -BB5

Hexadecimal: -6b9

Square: 2961841

Square Root: 41.48493702538308

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

Row sums of a number triangle related to the Pell numbers. A110331

a(n) = (n⁵ - 133·n⁴ + 6729·n³ - 158379·n² + 1720294·n - 6823316)/4. A121887

a(n) = 7 + 12·n - 6·n². A157517

Triangle T(n,k) = A015442(k) - A015442(n) + A015442(n-k) read by rows. A176264

Dirichlet g.f.: ζ(s) / (ζ(s-1) * ζ(s-2)). A351654

a(n) = n + (n+1)². A28387

Primes whose decimal representation is a valid number in base 8 and interpreted as such is again a prime. A235394

Partial sums of primes, if 1 is regarded as a prime (as it was until quite recently, see A008578). A14284

Primes of the form k² - k - 1. A2327

Greatest number of multisets that can be obtained by choosing a divisor of each part of an integer partition of n. A370808