644326257 has 4 divisors (see below), whose sum is σ = 859101680. Its totient is φ = 429550836.

The previous prime is 644326237. The next prime is 644326343. The reversal of 644326257 is 752623446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 644326257 - 2¹⁰ = 644325233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644326237) 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, 107387707 + ... + 107387712.

It is an arithmetic number, because the mean of its divisors is an integer number (214775420).

Almost surely, 2^644326257 is an apocalyptic number.

It is an amenable number.

644326257 is a deficient number, since it is larger than the sum of its proper divisors (214775423).

644326257 is a wasteful number, since it uses less digits than its factorization.

644326257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214775422.

The product of its digits is 241920, while the sum is 39.

The square root of 644326257 is about 25383.5824303820. The cubic root of 644326257 is about 863.7113166097.

The spelling of 644326257 in words is "six hundred forty-four million, three hundred twenty-six thousand, two hundred fifty-seven".