644860 has 24 divisors (see below), whose sum is σ = 1426320. Its totient is φ = 244224.

The previous prime is 644857. The next prime is 644863. The reversal of 644860 is 68446.

It is an interprime number because it is at equal distance from previous prime (644857) and next prime (644863).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 469 + ... + 1228.

It is an arithmetic number, because the mean of its divisors is an integer number (59430).

2⁶⁴⁴⁸⁶⁰ is an apocalyptic number.

It is an amenable number.

644860 is an abundant number, since it is smaller than the sum of its proper divisors (781460).

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

644860 is a wasteful number, since it uses less digits than its factorization.

644860 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1725 (or 1723 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 28.

The square root of 644860 is about 803.0317552874. The cubic root of 644860 is about 86.3949742733.

The spelling of 644860 in words is "six hundred forty-four thousand, eight hundred sixty".