644623923 has 4 divisors (see below), whose sum is σ = 859498568. Its totient is φ = 429749280.

The previous prime is 644623907. The next prime is 644623939. The reversal of 644623923 is 329326446.

644623923 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is an interprime number because it is at equal distance from previous prime (644623907) and next prime (644623939).

It is not a de Polignac number, because 644623923 - 2⁴ = 644623907 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644623943) 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, 107437318 + ... + 107437323.

It is an arithmetic number, because the mean of its divisors is an integer number (214874642).

Almost surely, 2^644623923 is an apocalyptic number.

644623923 is a deficient number, since it is larger than the sum of its proper divisors (214874645).

644623923 is a wasteful number, since it uses less digits than its factorization.

644623923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214874644.

The product of its digits is 186624, while the sum is 39.

The square root of 644623923 is about 25389.4451101240. The cubic root of 644623923 is about 863.8443019873.

It can be divided in two parts, 644623 and 923, that added together give a palindrome (645546).

The spelling of 644623923 in words is "six hundred forty-four million, six hundred twenty-three thousand, nine hundred twenty-three".