644669760 has 448 divisors, whose sum is σ = 2523451392. Its totient is φ = 136249344.

The previous prime is 644669747. The next prime is 644669771. The reversal of 644669760 is 67966446.

644669760 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (448).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 6646032 + ... + 6646128.

It is an arithmetic number, because the mean of its divisors is an integer number (5632704).

Almost surely, 2^644669760 is an apocalyptic number.

644669760 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 644669760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1261725696).

644669760 is an abundant number, since it is smaller than the sum of its proper divisors (1878781632).

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

644669760 is a wasteful number, since it uses less digits than its factorization.

644669760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 190 (or 180 counting only the distinct ones).

The product of its (nonzero) digits is 1306368, while the sum is 48.

The square root of 644669760 is about 25390.3477723327. The cubic root of 644669760 is about 863.8647765055.

The spelling of 644669760 in words is "six hundred forty-four million, six hundred sixty-nine thousand, seven hundred sixty".