Properties of the Number 1638

One Thousand Six Hundred Thirty-Eight

Basics

Value: 1637 → 1638 → 1639

Parity: even

Prime: No

Previous Prime: 1637

Next Prime: 1657

Digit Sum: 18

Digital Root: 9

Palindrome: No

Factorization: 2 × 3 ² × 7 × 13

Divisors: 1, 2, 3, 6, 7, 9, 13, 14, 18, 21

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

4823 Try Today's Challenge

Representations

Binary: 11001100110

Octal: 3146

Duodecimal: B46

Hexadecimal: 666

Square: 2683044

Square Root: 40.47221268969612

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

Catalan's triangle T(n,k) (read by rows): each term is the sum of the entries above and to the left, i.e., T(n,k) = ∑_j=0..k T(n-1,j). A9766

Harmonic or Ore numbers: numbers k such that the harmonic mean of the divisors of k is an integer. A1599

Triangle formed from odd-numbered columns of triangle of expansions of powers of·in terms of Chebyshev polynomials U_n(x). Sometimes called Catalan's triangle. A39598

a(n) = n*(n+3). A28552

Number of subsets of {1, ..., n} that are not sum-free. A88809

a(n) = n*(n+1)*(2·n+1)/3. A6331

G.f.: ∏_k>=1 (1 + 2·x^k). A32302

Number of permutations of [n+1] with exactly 1 increasing subsequence of length 3. A3517

Expansion of (1+x²)/((1-x)²*(1-x²)²). A5993

Catalan triangle read by rows. Also triangle of expansions of powers of·in terms of Chebyshev polynomials U_n(x). A8315