644828863 has 4 divisors (see below), whose sum is σ = 736947280. Its totient is φ = 552710448.

The previous prime is 644828831. The next prime is 644828879. The reversal of 644828863 is 368828446.

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 644828863 - 2⁵ = 644828831 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 (644828813) 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, 46059198 + ... + 46059211.

It is an arithmetic number, because the mean of its divisors is an integer number (184236820).

Almost surely, 2^644828863 is an apocalyptic number.

644828863 is a deficient number, since it is larger than the sum of its proper divisors (92118417).

644828863 is an equidigital number, since it uses as much as digits as its factorization.

644828863 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92118416.

The product of its digits is 1769472, while the sum is 49.

The square root of 644828863 is about 25393.4807184836. The cubic root of 644828863 is about 863.9358372670.

The spelling of 644828863 in words is "six hundred forty-four million, eight hundred twenty-eight thousand, eight hundred sixty-three".