644984 has 16 divisors (see below), whose sum is σ = 1242600. Its totient is φ = 313632.

The previous prime is 644977. The next prime is 644999. The reversal of 644984 is 489446.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644984.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 794 + ... + 1385.

2⁶⁴⁴⁹⁸⁴ is an apocalyptic number.

It is an amenable number.

644984 is a deficient number, since it is larger than the sum of its proper divisors (597616).

644984 is a wasteful number, since it uses less digits than its factorization.

644984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2222 (or 2218 counting only the distinct ones).

The product of its digits is 27648, while the sum is 35.

The square root of 644984 is about 803.1089589838. The cubic root of 644984 is about 86.4005115425.

The spelling of 644984 in words is "six hundred forty-four thousand, nine hundred eighty-four".