644387 has 4 divisors (see below), whose sum is σ = 647856. Its totient is φ = 640920.

The previous prime is 644383. The next prime is 644401. The reversal of 644387 is 783446.

It is a happy number.

644387 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644387 - 2² = 644383 is a prime.

It is a Duffinian 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 3 ways as a sum of consecutive naturals, for example, 1439 + ... + 1832.

It is an arithmetic number, because the mean of its divisors is an integer number (161964).

2⁶⁴⁴³⁸⁷ is an apocalyptic number.

644387 is a deficient number, since it is larger than the sum of its proper divisors (3469).

644387 is a wasteful number, since it uses less digits than its factorization.

644387 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3468.

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

The square root of 644387 is about 802.7371923612. The cubic root of 644387 is about 86.3738457502.

The spelling of 644387 in words is "six hundred forty-four thousand, three hundred eighty-seven".