6445 has 4 divisors (see below), whose sum is σ = 7740. Its totient is φ = 5152.

The previous prime is 6427. The next prime is 6449. The reversal of 6445 is 5446.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3844 + 2601 = 62^2 + 51^2 .

It is a cyclic number.

It is not a de Polignac number, because 6445 - 2⁷ = 6317 is a prime.

It is a plaindrome in base 8.

It is a nialpdrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 640 + ... + 649.

It is an arithmetic number, because the mean of its divisors is an integer number (1935).

2⁶⁴⁴⁵ is an apocalyptic number.

It is an amenable number.

6445 is a deficient number, since it is larger than the sum of its proper divisors (1295).

6445 is a wasteful number, since it uses less digits than its factorization.

6445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1294.

The product of its digits is 480, while the sum is 19.

The square root of 6445 is about 80.2807573457. The cubic root of 6445 is about 18.6097686383.

Subtracting from 6445 its reverse (5446), we obtain a palindrome (999).

The spelling of 6445 in words is "six thousand, four hundred forty-five".