644628 has 12 divisors (see below), whose sum is σ = 1504160. Its totient is φ = 214872.

The previous prime is 644617. The next prime is 644629. The reversal of 644628 is 826446.

It is a tau number, because it is divible by the number of its divisors (12).

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a plaindrome in base 14.

It is a junction number, because it is equal to n+sod(n) for n = 644595 and 644604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644629) by changing a digit.

644628 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, 26848 + ... + 26871.

2⁶⁴⁴⁶²⁸ is an apocalyptic number.

It is an amenable number.

644628 is an abundant number, since it is smaller than the sum of its proper divisors (859532).

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

644628 is a wasteful number, since it uses less digits than its factorization.

644628 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53726 (or 53724 counting only the distinct ones).

The product of its digits is 9216, while the sum is 30.

The square root of 644628 is about 802.8872897238. The cubic root of 644628 is about 86.3846123145.

The spelling of 644628 in words is "six hundred forty-four thousand, six hundred twenty-eight".