6400840 has 32 divisors (see below), whose sum is σ = 15250680. Its totient is φ = 2409472.

The previous prime is 6400837. The next prime is 6400841. The reversal of 6400840 is 480046.

It can be written as a sum of positive squares in 4 ways, for example, as 6380676 + 20164 = 2526^2 + 142^2 .

It is not an unprimeable number, because it can be changed into a prime (6400841) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4027 + ... + 5386.

Almost surely, 2^6400840 is an apocalyptic number.

It is an amenable number.

6400840 is an abundant number, since it is smaller than the sum of its proper divisors (8849840).

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

6400840 is a wasteful number, since it uses less digits than its factorization.

6400840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9441 (or 9437 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 22.

The square root of 6400840 is about 2529.9881422647. The cubic root of 6400840 is about 185.6716757696.

Adding to 6400840 its reverse (480046), we get a palindrome (6880886).

The spelling of 6400840 in words is "six million, four hundred thousand, eight hundred forty".