644662909 has 16 divisors (see below), whose sum is σ = 718502400. Its totient is φ = 573498160.

The previous prime is 644662897. The next prime is 644662939. The reversal of 644662909 is 909266446.

It is a cyclic number.

It is not a de Polignac number, because 644662909 - 2¹⁷ = 644531837 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644662939) 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 15 ways as a sum of consecutive naturals, for example, 94392 + ... + 100990.

It is an arithmetic number, because the mean of its divisors is an integer number (44906400).

Almost surely, 2^644662909 is an apocalyptic number.

It is an amenable number.

644662909 is a deficient number, since it is larger than the sum of its proper divisors (73839491).

644662909 is a wasteful number, since it uses less digits than its factorization.

644662909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6800.

The product of its (nonzero) digits is 559872, while the sum is 46.

The square root of 644662909 is about 25390.2128585012. The cubic root of 644662909 is about 863.8617163555.

The spelling of 644662909 in words is "six hundred forty-four million, six hundred sixty-two thousand, nine hundred nine".