644378013 has 24 divisors (see below), whose sum is σ = 986484096. Its totient is φ = 403920000.

The previous prime is 644378011. The next prime is 644378023. The reversal of 644378013 is 310873446.

644378013 is a `hidden beast` number, since 644 + 3 + 7 + 8 + 0 + 1 + 3 = 666.

It is not a de Polignac number, because 644378013 - 2¹ = 644378011 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644378011) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 285138 + ... + 287388.

It is an arithmetic number, because the mean of its divisors is an integer number (41103504).

Almost surely, 2^644378013 is an apocalyptic number.

It is an amenable number.

644378013 is a deficient number, since it is larger than the sum of its proper divisors (342106083).

644378013 is a wasteful number, since it uses less digits than its factorization.

644378013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4145 (or 4142 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 36.

The square root of 644378013 is about 25384.6018877586. The cubic root of 644378013 is about 863.7344420815.

The spelling of 644378013 in words is "six hundred forty-four million, three hundred seventy-eight thousand, thirteen".