644663163 has 4 divisors (see below), whose sum is σ = 859550888. Its totient is φ = 429775440.

The previous prime is 644663161. The next prime is 644663203. The reversal of 644663163 is 361366446.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 644663163 - 2¹ = 644663161 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644663161) 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, 107443858 + ... + 107443863.

It is an arithmetic number, because the mean of its divisors is an integer number (214887722).

Almost surely, 2^644663163 is an apocalyptic number.

644663163 is a deficient number, since it is larger than the sum of its proper divisors (214887725).

644663163 is a wasteful number, since it uses less digits than its factorization.

644663163 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214887724.

The product of its digits is 186624, while the sum is 39.

The square root of 644663163 is about 25390.2178604281. The cubic root of 644663163 is about 863.8618298105.

The spelling of 644663163 in words is "six hundred forty-four million, six hundred sixty-three thousand, one hundred sixty-three".