6642640 has 40 divisors (see below), whose sum is σ = 15811488. Its totient is φ = 2593920.

The previous prime is 6642637. The next prime is 6642659. The reversal of 6642640 is 462466.

It is a tau number, because it is divible by the number of its divisors (40).

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 6642599 and 6642608.

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, 2475 + ... + 4405.

Almost surely, 2^6642640 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 6642640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (7905744).

6642640 is an abundant number, since it is smaller than the sum of its proper divisors (9168848).

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

6642640 is a wasteful number, since it uses less digits than its factorization.

6642640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1987 (or 1981 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 28.

The square root of 6642640 is about 2577.3319537848. The cubic root of 6642640 is about 187.9808340202.

It can be divided in two parts, 66426 and 40, that added together give a palindrome (66466).

The spelling of 6642640 in words is "six million, six hundred forty-two thousand, six hundred forty".