Properties of the Number 20980

Twenty Thousand Nine Hundred Eighty

Basics

Value: 20979 → 20980 → 20981

Parity: even

Prime: No

Previous Prime: 20963

Next Prime: 20981

Digit Sum: 19

Digital Root: 1

Palindrome: No

Factorization: 2 ² × 5 × 1049

Divisors: 1, 2, 4, 5, 10, 20, 1049, 2098, 4196, 5245

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101000111110100

Octal: 50764

Duodecimal: 10184

Hexadecimal: 51f4

Square: 440160400

Square Root: 144.84474446799925

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

T(n,k) is the number of permutations of [n] having exactly k pairs of integers i<j in [n] such that their cycle minima have opposite sorting order; triangle T(n,k), n>=0, 0<=k<=A125811(n)-1, read by rows. A381529

Let M(n) be the n X n matrix m(i,j)=min(i,j) for 1<=i,j<=n; then a(n) is the trace of M(n)^-7. A114359

Expansion of g.f.: 1/((1 - x² - x³ - x⁴ - x⁵ - x⁶ - x⁷)*(1 + x + x² + x³ + x⁴ + x⁵ - x⁷)). A147605

Number of ways to partition n into reduced fractions i/j with j <= n. A154886

a(n) = 1000·n - 20. A157515

Row sums of A050157. A296771

Number of cells in a regular 7-gon after n generations of mitosis. A349808

Number of degree n polynomials p(x,y) with all coefficients 0 or 1 such that x+y=1 implies p(x,y)=1. A181496

a(n) = ∑_{k=0..floor((n+1)/2)} (k+1) * A008315(n, k). A27305

Least K such that K*(3^n+j)+1 is prime for j=0 to 4. A109854