Properties of the Number 21381

Twenty-One Thousand Three Hundred Eighty-One

Basics

Value: 21380 → 21381 → 21382

Parity: odd

Prime: No

Previous Prime: 21379

Next Prime: 21383

Digit Sum: 15

Digital Root: 6

Palindrome: No

Factorization: 3 × 7127

Divisors: 1, 3, 7127, 21381

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101001110000101

Octal: 51605

Duodecimal: 10459

Hexadecimal: 5385

Square: 457147161

Square Root: 146.2224332994086

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

Total number of parts coprime to n in the partitions of n into 7 parts. A363325

Integers k such that k·28·c + 1 is prime for c = 1, 2, 4, 7 and 14. A67199

Euler transform of A016116 = 2^floor(n/2). A392561

a(n) = p² - sum of digits of p^p, where p = prime(n). A140499

The number of lattice points in the 2D plane contained between the curve y=x²/4 and the line y=n², inclusive, where n is a positive integer. A385730

Expansion of 1/(1-x-x²-x³-x⁴+x⁵+x⁶+x⁷). A257934

Least number k = concat(x,y) such that k = n*(x+y) - x·y , -1 if such a number does not exist. A279058

Decimal expansion of 1/377. A21381