644120245 has 16 divisors (see below), whose sum is σ = 795257280. Its totient is φ = 500632704.

The previous prime is 644120237. The next prime is 644120249. The reversal of 644120245 is 542021446.

It is a cyclic number.

It is not a de Polignac number, because 644120245 - 2³ = 644120237 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644120249) 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, 11286 + ... + 37624.

It is an arithmetic number, because the mean of its divisors is an integer number (49703580).

Almost surely, 2^644120245 is an apocalyptic number.

It is an amenable number.

644120245 is a deficient number, since it is larger than the sum of its proper divisors (151137035).

644120245 is a wasteful number, since it uses less digits than its factorization.

644120245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26484.

The product of its (nonzero) digits is 7680, while the sum is 28.

The square root of 644120245 is about 25379.5241287145. The cubic root of 644120245 is about 863.6192546246.

The spelling of 644120245 in words is "six hundred forty-four million, one hundred twenty thousand, two hundred forty-five".