Properties of the Number 1721

One Thousand Seven Hundred Twenty-One

Basics

Value: 1720 → 1721 → 1722

Parity: odd

Prime: Yes

Previous Prime: 1709

Next Prime: 1723

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

Today's Target

4823 Try Today's Challenge

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

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

Moebius transform of A064987, n*σ(n). A69097

a(n) = n² - n - 1. A165900

Primes of the form x² + 40y². A107145

Mountain numbers. A134941

Primes of the form 16n+9. A105126