644495760 has 60 divisors (see below), whose sum is σ = 2164434012. Its totient is φ = 171865344.

The previous prime is 644495737. The next prime is 644495767. The reversal of 644495760 is 67594446.

It can be written as a sum of positive squares in 2 ways, for example, as 115863696 + 528632064 = 10764^2 + 22992^2 .

It is a tau number, because it is divible by the number of its divisors (60).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (644495767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 446847 + ... + 448286.

Almost surely, 2^644495760 is an apocalyptic number.

644495760 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644495760 is an abundant number, since it is smaller than the sum of its proper divisors (1519938252).

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

644495760 is a wasteful number, since it uses less digits than its factorization.

644495760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 895152 (or 895143 counting only the distinct ones).

The product of its (nonzero) digits is 725760, while the sum is 45.

The square root of 644495760 is about 25386.9210421429. The cubic root of 644495760 is about 863.7870488554.

The spelling of 644495760 in words is "six hundred forty-four million, four hundred ninety-five thousand, seven hundred sixty".