6821440 has 28 divisors (see below), whose sum is σ = 16244316. Its totient is φ = 2728448.

The previous prime is 6821407. The next prime is 6821443. The reversal of 6821440 is 441286.

It can be written as a sum of positive squares in 2 ways, for example, as 5419584 + 1401856 = 2328^2 + 1184^2 .

It is not an unprimeable number, because it can be changed into a prime (6821443) 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, 10339 + ... + 10978.

Almost surely, 2^6821440 is an apocalyptic number.

It is an amenable number.

6821440 is an abundant number, since it is smaller than the sum of its proper divisors (9422876).

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

6821440 is a wasteful number, since it uses less digits than its factorization.

6821440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21334 (or 21324 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 25.

The square root of 6821440 is about 2611.7886591376. The cubic root of 6821440 is about 189.6525506088.

The spelling of 6821440 in words is "six million, eight hundred twenty-one thousand, four hundred forty".