644057263 has 4 divisors (see below), whose sum is σ = 644346648. Its totient is φ = 643767880.

The previous prime is 644057251. The next prime is 644057273. The reversal of 644057263 is 362750446.

644057263 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 362750446 = 2 ⋅181375223.

It is a cyclic number.

It is not a de Polignac number, because 644057263 - 2¹⁷ = 643926191 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644057203) 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, 141328 + ... + 145813.

It is an arithmetic number, because the mean of its divisors is an integer number (161086662).

Almost surely, 2^644057263 is an apocalyptic number.

644057263 is a deficient number, since it is larger than the sum of its proper divisors (289385).

644057263 is a wasteful number, since it uses less digits than its factorization.

644057263 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 289384.

The product of its (nonzero) digits is 120960, while the sum is 37.

The square root of 644057263 is about 25378.2832949749. The cubic root of 644057263 is about 863.5911055115.

The spelling of 644057263 in words is "six hundred forty-four million, fifty-seven thousand, two hundred sixty-three".