644879945 has 16 divisors (see below), whose sum is σ = 779023872. Its totient is φ = 512472000.

The previous prime is 644879941. The next prime is 644879947. The reversal of 644879945 is 549978446.

It is not a de Polignac number, because 644879945 - 2² = 644879941 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644879941) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 858320 + ... + 859070.

It is an arithmetic number, because the mean of its divisors is an integer number (48688992).

Almost surely, 2^644879945 is an apocalyptic number.

It is an amenable number.

644879945 is a deficient number, since it is larger than the sum of its proper divisors (134143927).

644879945 is a wasteful number, since it uses less digits than its factorization.

644879945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1672.

The product of its digits is 8709120, while the sum is 56.

The square root of 644879945 is about 25394.4865079017. The cubic root of 644879945 is about 863.9586497307.

The spelling of 644879945 in words is "six hundred forty-four million, eight hundred seventy-nine thousand, nine hundred forty-five".