644046257 has 4 divisors (see below), whose sum is σ = 648311616. Its totient is φ = 639780900.

The previous prime is 644046209. The next prime is 644046259. The reversal of 644046257 is 752640446.

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 a cyclic number.

It is not a de Polignac number, because 644046257 - 2²⁶ = 576937393 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644046257.

It is not an unprimeable number, because it can be changed into a prime (644046259) 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, 2132453 + ... + 2132754.

It is an arithmetic number, because the mean of its divisors is an integer number (162077904).

Almost surely, 2^644046257 is an apocalyptic number.

It is an amenable number.

644046257 is a deficient number, since it is larger than the sum of its proper divisors (4265359).

644046257 is a wasteful number, since it uses less digits than its factorization.

644046257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4265358.

The product of its (nonzero) digits is 161280, while the sum is 38.

The square root of 644046257 is about 25378.0664551104. The cubic root of 644046257 is about 863.5861863123.

The spelling of 644046257 in words is "six hundred forty-four million, forty-six thousand, two hundred fifty-seven".