644686 has 8 divisors (see below), whose sum is σ = 1105200. Its totient is φ = 276288.

The previous prime is 644671. The next prime is 644687. The reversal of 644686 is 686446.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23011 + ... + 23038.

It is an arithmetic number, because the mean of its divisors is an integer number (138150).

2⁶⁴⁴⁶⁸⁶ is an apocalyptic number.

644686 is a deficient number, since it is larger than the sum of its proper divisors (460514).

644686 is a wasteful number, since it uses less digits than its factorization.

644686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46058.

The product of its digits is 27648, while the sum is 34.

The square root of 644686 is about 802.9234085515. The cubic root of 644686 is about 86.3872030373.

The spelling of 644686 in words is "six hundred forty-four thousand, six hundred eighty-six".