6821640 has 96 divisors (see below), whose sum is σ = 25346880. Its totient is φ = 1558656.

The previous prime is 6821629. The next prime is 6821663. The reversal of 6821640 is 461286.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1167 + ... + 3873.

It is an arithmetic number, because the mean of its divisors is an integer number (264030).

Almost surely, 2^6821640 is an apocalyptic number.

6821640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6821640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (12673440).

6821640 is an abundant number, since it is smaller than the sum of its proper divisors (18525240).

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

6821640 is a wasteful number, since it uses less digits than its factorization.

6821640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2731 (or 2724 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 6821640 is about 2611.8269467941. The cubic root of 6821640 is about 189.6544040854.

The spelling of 6821640 in words is "six million, eight hundred twenty-one thousand, six hundred forty".