644790 has 16 divisors (see below), whose sum is σ = 1547568. Its totient is φ = 171936.

The previous prime is 644789. The next prime is 644797. The reversal of 644790 is 97446.

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 21493 = 644790 / (6 + 4 + 4 + 7 + 9 + 0).

It is a congruent number.

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

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10717 + ... + 10776.

It is an arithmetic number, because the mean of its divisors is an integer number (96723).

2⁶⁴⁴⁷⁹⁰ is an apocalyptic number.

644790 is an abundant number, since it is smaller than the sum of its proper divisors (902778).

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

644790 is a wasteful number, since it uses less digits than its factorization.

644790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21503.

The product of its (nonzero) digits is 6048, while the sum is 30.

The square root of 644790 is about 802.9881692777. The cubic root of 644790 is about 86.3918480820.

The spelling of 644790 in words is "six hundred forty-four thousand, seven hundred ninety".