644753923 has 8 divisors (see below), whose sum is σ = 740387520. Its totient is φ = 555290280.

The previous prime is 644753899. The next prime is 644753927. The reversal of 644753923 is 329357446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644753923 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644753923.

It is not an unprimeable number, because it can be changed into a prime (644753927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1542265 + ... + 1542682.

It is an arithmetic number, because the mean of its divisors is an integer number (92548440).

Almost surely, 2^644753923 is an apocalyptic number.

644753923 is a deficient number, since it is larger than the sum of its proper divisors (95633597).

644753923 is a wasteful number, since it uses less digits than its factorization.

644753923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3084977.

The product of its digits is 544320, while the sum is 43.

The square root of 644753923 is about 25392.0051000310. The cubic root of 644753923 is about 863.9023679939.

The spelling of 644753923 in words is "six hundred forty-four million, seven hundred fifty-three thousand, nine hundred twenty-three".