644861760 has 112 divisors (see below), whose sum is σ = 2076492672. Its totient is φ = 169523200.

The previous prime is 644861747. The next prime is 644861797. The reversal of 644861760 is 67168446.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 63430 + ... + 72890.

Almost surely, 2^644861760 is an apocalyptic number.

644861760 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644861760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1038246336).

644861760 is an abundant number, since it is smaller than the sum of its proper divisors (1431630912).

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

644861760 is a wasteful number, since it uses less digits than its factorization.

644861760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9552 (or 9542 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 42.

The square root of 644861760 is about 25394.1284552158. The cubic root of 644861760 is about 863.9505287175.

The spelling of 644861760 in words is "six hundred forty-four million, eight hundred sixty-one thousand, seven hundred sixty".