644390 has 8 divisors (see below), whose sum is σ = 1159920. Its totient is φ = 257752.

The previous prime is 644383. The next prime is 644401. The reversal of 644390 is 93446.

644390 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 a congruent number.

It is an unprimeable number.

644390 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32210 + ... + 32229.

It is an arithmetic number, because the mean of its divisors is an integer number (144990).

2⁶⁴⁴³⁹⁰ is an apocalyptic number.

644390 is a deficient number, since it is larger than the sum of its proper divisors (515530).

644390 is a wasteful number, since it uses less digits than its factorization.

644390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64446.

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 644390 is about 802.7390609656. The cubic root of 644390 is about 86.3739797903.

The spelling of 644390 in words is "six hundred forty-four thousand, three hundred ninety".