644828 has 24 divisors (see below), whose sum is σ = 1212288. Its totient is φ = 299376.

The previous prime is 644801. The next prime is 644837. The reversal of 644828 is 828446.

It is an Ulam number.

644828 is a modest number, since divided by 828 gives 644 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 644794 and 644803.

It is a congruent number.

It is an unprimeable number.

644828 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 7 ways as a sum of consecutive naturals, for example, 3875 + ... + 4037.

It is an arithmetic number, because the mean of its divisors is an integer number (50512).

2⁶⁴⁴⁸²⁸ is an apocalyptic number.

It is an amenable number.

644828 is a deficient number, since it is larger than the sum of its proper divisors (567460).

644828 is a wasteful number, since it uses less digits than its factorization.

644828 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 233 (or 231 counting only the distinct ones).

The product of its digits is 12288, while the sum is 32.

The square root of 644828 is about 803.0118305480. The cubic root of 644828 is about 86.3935451854.

The spelling of 644828 in words is "six hundred forty-four thousand, eight hundred twenty-eight".