Properties of the Number 21400

Twenty-One Thousand Four Hundred

Basics

Value: 21399 → 21400 → 21401

Parity: even

Prime: No

Previous Prime: 21397

Next Prime: 21401

Digit Sum: 7

Digital Root: 7

Palindrome: No

Factorization: 2 ³ × 5 ² × 107

Divisors: 1, 2, 4, 5, 8, 10, 20, 25, 40, 50

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101001110011000

Octal: 51630

Duodecimal: 10474

Hexadecimal: 5398

Square: 457960000

Square Root: 146.28738838327794

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

Otto Haxel's guess for magic numbers of nuclear shells. A33547

G.f. A(x) satisfies 1/x = ∑_n=-oo..+oo A(x)ⁿ * (1 + A(x)ⁿ)ⁿ⁺¹. A378264

Expansion of g²/(1 - x²*g⁶), where g = 1+x·g⁴ is the g.f. of A002293. A391084

Underline the central digit of all terms: the underlined digits reconstruct the starting sequence. This is also true if one translates the sequence in French and underlines the central letter of each word: the underlined letters spell the (French) sequence again. This is the lexicographically earliest sequence where repeated terms are admitted. A319718

If 0 <= n <= 3 then a(n) = n(n+1)(n+2)/3, if n >= 4 then a(n) = n(n²+5)/3. A162626

a(n) = A002704(n)/2. A262570

a(n) = ∑_k=1..n k·rad(k). A350996

f-vectors for simplicial complexes of dimension at most 2 on at most n-1 vertices. A11827

Lengths of runs of the initial digits of semiprimes in decimal representation, cf. A239634. A239639

Numbers that are not the difference of two binary palindromes (A006995). A290393