644378 has 8 divisors (see below), whose sum is σ = 1104672. Its totient is φ = 276156.

The previous prime is 644377. The next prime is 644381. The reversal of 644378 is 873446.

Added to its reverse (873446) it gives a square (1517824 = 1232²).

It is a happy number.

644378 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (644377) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23000 + ... + 23027.

It is an arithmetic number, because the mean of its divisors is an integer number (138084).

2⁶⁴⁴³⁷⁸ is an apocalyptic number.

644378 is a deficient number, since it is larger than the sum of its proper divisors (460294).

644378 is a wasteful number, since it uses less digits than its factorization.

644378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46036.

The product of its digits is 16128, while the sum is 32.

The square root of 644378 is about 802.7315865219. The cubic root of 644378 is about 86.3734436273.

Adding to 644378 its reverse (873446), we get a square (1517824 = 1232²).

The spelling of 644378 in words is "six hundred forty-four thousand, three hundred seventy-eight".