644684667 has 32 divisors (see below), whose sum is σ = 950932224. Its totient is φ = 385257600.

The previous prime is 644684657. The next prime is 644684669. The reversal of 644684667 is 766486446.

It is not a de Polignac number, because 644684667 - 2⁶ = 644684603 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644684669) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 851253 + ... + 852009.

It is an arithmetic number, because the mean of its divisors is an integer number (29716632).

Almost surely, 2^644684667 is an apocalyptic number.

644684667 is a deficient number, since it is larger than the sum of its proper divisors (306247557).

644684667 is a wasteful number, since it uses less digits than its factorization.

644684667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1099.

The product of its digits is 4644864, while the sum is 51.

The square root of 644684667 is about 25390.6413270717. The cubic root of 644684667 is about 863.8714349704.

The spelling of 644684667 in words is "six hundred forty-four million, six hundred eighty-four thousand, six hundred sixty-seven".