644796 has 18 divisors (see below), whose sum is σ = 1629992. Its totient is φ = 214920.

The previous prime is 644789. The next prime is 644797. The reversal of 644796 is 697446.

644796 is a `hidden beast` number, since 644 + 7 + 9 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 17911 = 644796 / (6 + 4 + 4 + 7 + 9 + 6).

It is a self number, because there is not a number n which added to its sum of digits gives 644796.

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 644796.

It is not an unprimeable number, because it can be changed into a prime (644797) by changing a digit.

644796 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 5 ways as a sum of consecutive naturals, for example, 8920 + ... + 8991.

2⁶⁴⁴⁷⁹⁶ is an apocalyptic number.

It is an amenable number.

644796 is an abundant number, since it is smaller than the sum of its proper divisors (985196).

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

644796 is a wasteful number, since it uses less digits than its factorization.

644796 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17921 (or 17916 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 644796 is about 802.9919053141. The cubic root of 644796 is about 86.3921160502.

Subtracting 644796 from its reverse (697446), we obtain a triangular number (52650 = T₃₂₄).

The spelling of 644796 in words is "six hundred forty-four thousand, seven hundred ninety-six".