644783039 has 4 divisors (see below), whose sum is σ = 645786456. Its totient is φ = 643779624.

The previous prime is 644783011. The next prime is 644783059. The reversal of 644783039 is 930387446.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644783039 - 2²⁰ = 643734463 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644783059) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 500744 + ... + 502029.

It is an arithmetic number, because the mean of its divisors is an integer number (161446614).

Almost surely, 2^644783039 is an apocalyptic number.

644783039 is a deficient number, since it is larger than the sum of its proper divisors (1003417).

644783039 is a wasteful number, since it uses less digits than its factorization.

644783039 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1003416.

The product of its (nonzero) digits is 435456, while the sum is 44.

The square root of 644783039 is about 25392.5784236261. The cubic root of 644783039 is about 863.9153719229.

The spelling of 644783039 in words is "six hundred forty-four million, seven hundred eighty-three thousand, thirty-nine".