644858653 has 4 divisors (see below), whose sum is σ = 645881248. Its totient is φ = 643836060.

The previous prime is 644858597. The next prime is 644858657. The reversal of 644858653 is 356858446.

It is a happy number.

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 644858653 - 2¹³ = 644850461 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644858597 and 644858606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644858657) by changing a digit.

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, 510351 + ... + 511612.

It is an arithmetic number, because the mean of its divisors is an integer number (161470312).

Almost surely, 2^644858653 is an apocalyptic number.

It is an amenable number.

644858653 is a deficient number, since it is larger than the sum of its proper divisors (1022595).

644858653 is a wasteful number, since it uses less digits than its factorization.

644858653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1022594.

The product of its digits is 2764800, while the sum is 49.

The square root of 644858653 is about 25394.0672795832. The cubic root of 644858653 is about 863.9491411857.

The spelling of 644858653 in words is "six hundred forty-four million, eight hundred fifty-eight thousand, six hundred fifty-three".