6442640 has 40 divisors (see below), whose sum is σ = 15501240. Its totient is φ = 2487296.

The previous prime is 6442633. The next prime is 6442661. The reversal of 6442640 is 462446.

6442640 = T₂₀₀ + T₂₀₁ + ... + T₃₅₉.

It can be written as a sum of positive squares in 4 ways, for example, as 132496 + 6310144 = 364^2 + 2512^2 .

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

It is a super-2 number, since 2×6442640² = 83015220339200, which contains 22 as substring.

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, 932 + ... + 3708.

It is an arithmetic number, because the mean of its divisors is an integer number (387531).

Almost surely, 2^6442640 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 6442640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (7750620).

6442640 is an abundant number, since it is smaller than the sum of its proper divisors (9058600).

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

6442640 is a wasteful number, since it uses less digits than its factorization.

6442640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2819 (or 2813 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 26.

The square root of 6442640 is about 2538.2356076614. The cubic root of 6442640 is about 186.0749688156.

The spelling of 6442640 in words is "six million, four hundred forty-two thousand, six hundred forty".