644534023 has 4 divisors (see below), whose sum is σ = 736610320. Its totient is φ = 552457728.

The previous prime is 644534021. The next prime is 644534027. The reversal of 644534023 is 320435446.

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 644534023 - 2¹ = 644534021 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 (644534021) 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, 46038138 + ... + 46038151.

It is an arithmetic number, because the mean of its divisors is an integer number (184152580).

Almost surely, 2^644534023 is an apocalyptic number.

644534023 is a deficient number, since it is larger than the sum of its proper divisors (92076297).

644534023 is an equidigital number, since it uses as much as digits as its factorization.

644534023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92076296.

The product of its (nonzero) digits is 34560, while the sum is 31.

The square root of 644534023 is about 25387.6746276614. The cubic root of 644534023 is about 863.8041425442.

Adding to 644534023 its reverse (320435446), we get a palindrome (964969469).

The spelling of 644534023 in words is "six hundred forty-four million, five hundred thirty-four thousand, twenty-three".