Properties of the Number 405

Four Hundred Five

Basics

Value: 404 → 405 → 406

Parity: odd

Prime: No

Previous Prime: 401

Next Prime: 409

Digit Sum: 9

Digital Root: 9

Palindrome: No

Factorization: 3 ⁴ × 5

Divisors: 1, 3, 5, 9, 15, 27, 45, 81, 135, 405

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 110010101

Octal: 625

Duodecimal: 299

Hexadecimal: 195

Square: 164025

Square Root: 20.12461179749811

Classification

Fibonacci: No

Bell Number: No

Factorial Number: No

Regular Number: Yes

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

Completely multiplicative with a(prime(k)) = prime(k+1). A3961

a(n) = n*(n+3)/2. A96

Pentagonal pyramidal numbers: a(n) = n²*(n+1)/2. A2411

5-smooth numbers, i.e., numbers whose prime divisors are all <= 5. A51037

Odd numbers of the form p^1+4k * r², where p is prime of the form 1+4m, r > 1, and gcd(p,r) = 1. (Euler's criteria for odd perfect numbers). A228058

Antisigma(n): Sum of the numbers less than n that do not divide n. A24816

Multiples of 9: a(n) = 9·n. A8591

Numbers that are products of 5 primes (or 5-almost primes, a generalization of semiprimes). A14614

Number of "ON" cells at n-th stage in the "Ulam-Warburton" two-dimensional cellular automaton. A147562

Numbers that are the sum of 3 positive cubes. A3072