644340245 has 4 divisors (see below), whose sum is σ = 773208300. Its totient is φ = 515472192.

The previous prime is 644340233. The next prime is 644340247. The reversal of 644340245 is 542043446.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 465610084 + 178730161 = 21578^2 + 13369^2 .

It is a cyclic number.

It is not a de Polignac number, because 644340245 - 2¹² = 644336149 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644340247) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64434020 + ... + 64434029.

It is an arithmetic number, because the mean of its divisors is an integer number (193302075).

Almost surely, 2^644340245 is an apocalyptic number.

It is an amenable number.

644340245 is a deficient number, since it is larger than the sum of its proper divisors (128868055).

644340245 is a wasteful number, since it uses less digits than its factorization.

644340245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128868054.

The product of its (nonzero) digits is 46080, while the sum is 32.

The square root of 644340245 is about 25383.8579613108. The cubic root of 644340245 is about 863.7175668111.

The spelling of 644340245 in words is "six hundred forty-four million, three hundred forty thousand, two hundred forty-five".