644855907 has 16 divisors (see below), whose sum is σ = 890954240. Its totient is φ = 414584352.

The previous prime is 644855863. The next prime is 644855921. The reversal of 644855907 is 709558446.

It is not a de Polignac number, because 644855907 - 2⁶ = 644855843 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644855927) 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, 21448 + ... + 41829.

It is an arithmetic number, because the mean of its divisors is an integer number (55684640).

Almost surely, 2^644855907 is an apocalyptic number.

644855907 is a deficient number, since it is larger than the sum of its proper divisors (246098333).

644855907 is a wasteful number, since it uses less digits than its factorization.

644855907 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63402.

The product of its (nonzero) digits is 1209600, while the sum is 48.

The square root of 644855907 is about 25394.0132117789. The cubic root of 644855907 is about 863.9479148664.

The spelling of 644855907 in words is "six hundred forty-four million, eight hundred fifty-five thousand, nine hundred seven".