644380 has 48 divisors (see below), whose sum is σ = 1542240. Its totient is φ = 224000.

The previous prime is 644377. The next prime is 644381. The reversal of 644380 is 83446.

644380 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644381) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6330 + ... + 6430.

It is an arithmetic number, because the mean of its divisors is an integer number (32130).

2⁶⁴⁴³⁸⁰ 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 644380, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (771120).

644380 is an abundant number, since it is smaller than the sum of its proper divisors (897860).

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

644380 is a wasteful number, since it uses less digits than its factorization.

644380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150 (or 148 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 25.

The square root of 644380 is about 802.7328322674. The cubic root of 644380 is about 86.3735329883.

It can be divided in two parts, 644 and 380, that added together give a 10-th power (1024 = 2¹⁰).

The spelling of 644380 in words is "six hundred forty-four thousand, three hundred eighty".