6440844640 has 48 divisors (see below), whose sum is σ = 15257431728. Its totient is φ = 2569406976.

The previous prime is 6440844623. The next prime is 6440844647. The reversal of 6440844640 is 464480446.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 6440844593 and 6440844602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6440844647) 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, 5719 + ... + 113641.

It is an arithmetic number, because the mean of its divisors is an integer number (317863161).

Almost surely, 2^6440844640 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 6440844640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (7628715864).

6440844640 is an abundant number, since it is smaller than the sum of its proper divisors (8816587088).

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

6440844640 is a wasteful number, since it uses less digits than its factorization.

6440844640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108311 (or 108303 counting only the distinct ones).

The product of its (nonzero) digits is 294912, while the sum is 40.

The square root of 6440844640 is about 80254.8729984666. The cubic root of 6440844640 is about 1860.5768280698.

The spelling of 6440844640 in words is "six billion, four hundred forty million, eight hundred forty-four thousand, six hundred forty".