Properties of the Number -721

Seven Hundred Twenty-One

Basics

Value: -722 → -721 → -720

Parity: odd

Prime: No

Previous Prime:

Next Prime: 1

Digit Sum: 10

Digital Root: 1

Palindrome: No

Factorization: 7 × 103

Divisors: 1, 7, 103, 721

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: -1011010001

Octal: -1321

Duodecimal: -501

Hexadecimal: -2d1

Square: 519841

Square Root: 26.851443164195103

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

Hafnian of a +/-1 array. A202038

Reflected tetranacci numbers A073817. A74058

a(n) = ∑_k=1..n μ(k)*k⁴. A336278

Square array A(n, k) = A246278(1+n, k) - 2·A246278(n, k), read by falling antidiagonals, where A246278 is the prime shift array. A372562

G.f.: 1/(1 + x - x² - x³ + x⁴). A199803

G.f.: 1/(1-2·x+2·x²-x³+x⁴). A199802

Triangle T(n, k) = T(n, k-1) + (-1)^k*A060187(n+2,k+1) if k <= floor(n/2), otherwise T(n, n-k), with T(n, 0) = T(n, n) = 1, read by rows. A225356

a(n) is the smallest error in trying to solve n⁴ = x⁴ + y⁴. That is, for each n from 2 on, find positive integers·and y, x <= y < n such that |n⁴ - x⁴ - y⁴| is minimal and let a(n) = n⁴ - x⁴ - y⁴. A308834

Dirichlet g.f.: ζ(s-2)² * (1 - 2^3-s) / ζ(s). A368929

sech(arctan(sin(x)))=1-1/2!*x²+17/4!*x⁴-721/6!*x⁶+58337/8!*x⁸... A12193