644978879 has 12 divisors (see below), whose sum is σ = 670704840. Its totient is φ = 620205600.

The previous prime is 644978869. The next prime is 644978881. The reversal of 644978879 is 978879446.

It is not a de Polignac number, because 644978879 - 2⁴ = 644978863 is a prime.

It is a super-3 number, since 3×644978879³ (a number of 27 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644978809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 224804 + ... + 227654.

It is an arithmetic number, because the mean of its divisors is an integer number (55892070).

Almost surely, 2^644978879 is an apocalyptic number.

644978879 is a deficient number, since it is larger than the sum of its proper divisors (25725961).

644978879 is a wasteful number, since it uses less digits than its factorization.

644978879 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3178 (or 3149 counting only the distinct ones).

The product of its digits is 24385536, while the sum is 62.

The square root of 644978879 is about 25396.4343757150. The cubic root of 644978879 is about 864.0028287623.

The spelling of 644978879 in words is "six hundred forty-four million, nine hundred seventy-eight thousand, eight hundred seventy-nine".