6645 has 8 divisors (see below), whose sum is σ = 10656. Its totient is φ = 3536.

The previous prime is 6637. The next prime is 6653. The reversal of 6645 is 5466.

6645 = 10² + 11² + ... + 27².

It is an interprime number because it is at equal distance from previous prime (6637) and next prime (6653).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 6645 - 2³ = 6637 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 207 + ... + 236.

It is an arithmetic number, because the mean of its divisors is an integer number (1332).

2⁶⁶⁴⁵ is an apocalyptic number.

It is an amenable number.

6645 is a deficient number, since it is larger than the sum of its proper divisors (4011).

6645 is a wasteful number, since it uses less digits than its factorization.

6645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 451.

The product of its digits is 720, while the sum is 21.

The square root of 6645 is about 81.5168694198. The cubic root of 6645 is about 18.8003093355.

Adding to 6645 its sum of digits (21), we get a palindrome (6666).

It can be divided in two parts, 66 and 45, that added together give a palindrome (111).

The spelling of 6645 in words is "six thousand, six hundred forty-five".