644906023 has 4 divisors (see below), whose sum is σ = 644962320. Its totient is φ = 644849728.

The previous prime is 644905951. The next prime is 644906047. The reversal of 644906023 is 320609446.

644906023 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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 644906023 - 2¹³ = 644897831 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 644906023.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644906063) 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, 4138 + ... + 36151.

It is an arithmetic number, because the mean of its divisors is an integer number (161240580).

Almost surely, 2^644906023 is an apocalyptic number.

644906023 is a deficient number, since it is larger than the sum of its proper divisors (56297).

644906023 is a wasteful number, since it uses less digits than its factorization.

644906023 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56296.

The product of its (nonzero) digits is 31104, while the sum is 34.

The square root of 644906023 is about 25394.9999606222. Note that the first 4 decimals coincide. The cubic root of 644906023 is about 863.9702953143.

The spelling of 644906023 in words is "six hundred forty-four million, nine hundred six thousand, twenty-three".