644251005 has 12 divisors (see below), whose sum is σ = 1116701820. Its totient is φ = 343600512.

The previous prime is 644250977. The next prime is 644251007. The reversal of 644251005 is 500152446.

644251005 is a `hidden beast` number, since 644 + 2 + 5 + 10 + 0 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 351225081 + 293025924 = 18741^2 + 17118^2 .

It is not a de Polignac number, because 644251005 - 2⁷ = 644250877 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644251005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644251007) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7158300 + ... + 7158389.

It is an arithmetic number, because the mean of its divisors is an integer number (93058485).

Almost surely, 2^644251005 is an apocalyptic number.

It is an amenable number.

644251005 is a deficient number, since it is larger than the sum of its proper divisors (472450815).

644251005 is a wasteful number, since it uses less digits than its factorization.

644251005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14316700 (or 14316697 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

The square root of 644251005 is about 25382.1000904181. The cubic root of 644251005 is about 863.6776905113.

The spelling of 644251005 in words is "six hundred forty-four million, two hundred fifty-one thousand, five".