6440645764 has 72 divisors (see below), whose sum is σ = 13632167808. Its totient is φ = 2607845760.

The previous prime is 6440645741. The next prime is 6440645797. The reversal of 6440645764 is 4675460446.

It is a super-2 number, since 2×6440645764² = 82963835714662287392, which contains 22 as substring.

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, 5265657 + ... + 5266879.

It is an arithmetic number, because the mean of its divisors is an integer number (189335664).

Almost surely, 2^6440645764 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 6440645764, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (6816083904).

6440645764 is an abundant number, since it is smaller than the sum of its proper divisors (7191522044).

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

6440645764 is a wasteful number, since it uses less digits than its factorization.

6440645764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1793 (or 1772 counting only the distinct ones).

The product of its (nonzero) digits is 1935360, while the sum is 46.

The square root of 6440645764 is about 80253.6339613354. The cubic root of 6440645764 is about 1860.5576779994.

The spelling of 6440645764 in words is "six billion, four hundred forty million, six hundred forty-five thousand, seven hundred sixty-four".