644373245 has 4 divisors (see below), whose sum is σ = 773247900. Its totient is φ = 515498592.

The previous prime is 644373227. The next prime is 644373251. The reversal of 644373245 is 542373446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 542373446 = 2 ⋅271186723.

It can be written as a sum of positive squares in 2 ways, for example, as 221741881 + 422631364 = 14891^2 + 20558^2 .

It is a cyclic number.

It is not a de Polignac number, because 644373245 - 2¹⁰ = 644372221 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644373199 and 644373208.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 64437320 + ... + 64437329.

It is an arithmetic number, because the mean of its divisors is an integer number (193311975).

Almost surely, 2^644373245 is an apocalyptic number.

It is an amenable number.

644373245 is a deficient number, since it is larger than the sum of its proper divisors (128874655).

644373245 is a wasteful number, since it uses less digits than its factorization.

644373245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128874654.

The product of its digits is 241920, while the sum is 38.

The square root of 644373245 is about 25384.5079723835. The cubic root of 644373245 is about 863.7323117088.

The spelling of 644373245 in words is "six hundred forty-four million, three hundred seventy-three thousand, two hundred forty-five".