6640 has 20 divisors (see below), whose sum is σ = 15624. Its totient is φ = 2624.

The previous prime is 6637. The next prime is 6653. The reversal of 6640 is 466.

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a nialpdrome in base 10.

It is a zygodrome in base 2.

It is a congruent number.

It is an unprimeable number.

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, 39 + ... + 121.

2⁶⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (7812).

6640 is an abundant number, since it is smaller than the sum of its proper divisors (8984).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

6640 is a wasteful number, since it uses less digits than its factorization.

6640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96 (or 90 counting only the distinct ones).

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

The square root of 6640 is about 81.4861951499. The cubic root of 6640 is about 18.7955927499.

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

The spelling of 6640 in words is "six thousand, six hundred forty".