6406 has 4 divisors (see below), whose sum is σ = 9612. Its totient is φ = 3202.

The previous prime is 6397. The next prime is 6421. The reversal of 6406 is 6046.

6406 is nontrivially palindromic in base 6.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6046 = 2 ⋅3023.

It is a self number, because there is not a number n which added to its sum of digits gives 6406.

It is a congruent number.

It is an unprimeable number.

6406 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1600 + ... + 1603.

It is an arithmetic number, because the mean of its divisors is an integer number (2403).

2⁶⁴⁰⁶ is an apocalyptic number.

6406 is a deficient number, since it is larger than the sum of its proper divisors (3206).

6406 is a wasteful number, since it uses less digits than its factorization.

6406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3205.

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 6406 is about 80.0374912151. The cubic root of 6406 is about 18.5721555083.

It can be divided in two parts, 640 and 6, that added together give a palindrome (646).

The spelling of 6406 in words is "six thousand, four hundred six".