644480 has 64 divisors (see below), whose sum is σ = 1652400. Its totient is φ = 239616.

The previous prime is 644447. The next prime is 644489. The reversal of 644480 is 84446.

It is a tau number, because it is divible by the number of its divisors (64).

It is a d-powerful number, because it can be written as 6⁷ + 4⁶ + 4⁸ + 4⁹ + 8⁵ + 0 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644489) 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, 12134 + ... + 12186.

2⁶⁴⁴⁴⁸⁰ 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 644480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (826200).

644480 is an abundant number, since it is smaller than the sum of its proper divisors (1007920).

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

644480 is a wasteful number, since it uses less digits than its factorization.

644480 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91 (or 79 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 26.

The square root of 644480 is about 802.7951170753. The cubic root of 644480 is about 86.3780008005.

The spelling of 644480 in words is "six hundred forty-four thousand, four hundred eighty".